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Transcript
Observing with SkyTools 3
Starter Edition
Greg Crinklaw
1
Copyright © 2012 Skyhound. All rights reserved.
Table of Contents
Getting Started in Astronomy ................................................................. 5
What SkyTools can do for you ............................................................. 7
Using the SkyTools Help System .......................................................... 7
Growing with the Hobby ..................................................................... 8
The Basics of Observing ........................................................................ 9
Equipment Basics .............................................................................. 9
Binoculars ...................................................................................... 9
Telescopes ..................................................................................... 9
Setting-Up SkyTools ......................................................................... 16
Magnitude of Faintest Star ............................................................. 16
Learning the Sky ............................................................................. 18
Sunrise and Sunset ....................................................................... 19
Constellations – Recognizing Star Patterns ....................................... 20
Observation Planning ....................................................................... 25
Using the Nightly Planner .................................................................. 28
Finding Targets in Binoculars ............................................................. 33
Finding Targets at the Telescope........................................................ 36
Using the SkyTools Finder Charts .................................................... 37
Observing Deep Sky Objects in the Telescope ..................................... 47
Keeping an Observing Log ................................................................ 49
Seek Out Your Local Astronomy Club.................................................. 49
Things to Look At in the Sky ................................................................ 50
The Bread and Butter of Backyard Astronomy ..................................... 50
The Moon ..................................................................................... 52
The Sun ....................................................................................... 55
The Stars ..................................................................................... 56
Jupiter ......................................................................................... 60
Venus and Mercury ....................................................................... 63
Saturn ......................................................................................... 67
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Mars ............................................................................................ 69
Naked-Eye Comets ........................................................................ 73
Open Clusters ............................................................................... 76
The Milky Way .............................................................................. 79
Easy Deep Sky Objects .................................................................. 79
Taking Backyard Observing to the Next Level ...................................... 83
Uranus and Neptune ...................................................................... 84
Globular Clusters .......................................................................... 85
Galaxies....................................................................................... 86
Diffuse Nebulas ............................................................................ 89
Planetary Nebulas ......................................................................... 90
Dark Nebulas ................................................................................ 91
Asteroids ..................................................................................... 93
Pluto ........................................................................................... 95
Telescopic Comets ........................................................................ 97
Novas .......................................................................................... 99
Supernovas ................................................................................ 101
Quasars ..................................................................................... 104
The Great Red Spot of Jupiter ....................................................... 105
Astronomy Nuts and Bolts ................................................................. 106
How Far is it? – Distances ............................................................... 106
How Big is it? – Sizing Things in the Sky ........................................... 107
How Bright is it? – Magnitudes ........................................................ 108
Where is it? – Celestial Coordinates ................................................. 109
What is it Called? – Astronomical Catalogs ........................................ 111
Build Your Own Scale Model of the Solar System .................................. 113
The Greek Alphabet .......................................................................... 116
The Constellations ............................................................................ 117
Selected Observing Resources ............................................................ 120
Handbooks .................................................................................... 120
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Copyright © 2012 Skyhound. All rights reserved.
Web Sites ..................................................................................... 120
Glossary .......................................................................................... 121
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Copyright © 2012 Skyhound. All rights reserved.
Getting Started in Astronomy
This guide is a combination of a beginner’s observing handbook and
SkyTools Starter Edition user’s manual. It will serve as an introduction to
viewing the night sky with binoculars and small telescopes, explaining how
SkyTools can help you as we go along. This is an observing handbook and
basic manual, but not a complete reference for using the program. For that
see the Help system within SkyTools.
There is a lot to backyard astronomy and it is easy to become overwhelmed
with the technical aspects of telescopes and the Universe. My advice is to
start slowly; learn how to use your binoculars or telescope and focus on
viewing the easier things in the sky, such as the moon, bright planets and
double stars. Later you can move on to the “faint fuzzies,” which are more
challenging to find and less dramatic to look at in the eyepiece.
The first thing to do is to start watching the sky, day and night, without
binoculars or telescope. Become aware of how the sky moves over 24 hours
and how the moon moves and changes from night to night. The light on the
moon is constantly changing, and you could spend a lifetime observing it
alone. Learn your local directions; where is north, south, east and west?
As you watch the sky change note any bright stars that catch your eye.
What direction is it in? At what time? Does it have a color? SkyTools will be
able to help you identify this star, and you may discover it is in fact a planet.
When you do find a planet, start watching it every night. Compare it to
nearby stars. Over time you will see it slowly move among them. Planet
means “wanderer” and for most of human history they were known merely
as wandering points of light.
The moon is the best target for your binoculars or telescope, so start looking
at it first. The next step is to point your telescope at a planet, once you find
one. This guide offers chapters about the moon and each planet, explaining
how to observe them and what you can expect to see.
In addition to looking at the moon, planets and stars, a good project is to
learn the constellations. SkyTools can make charts for you that show stick
figures to help you identify them. This is the first and most important step
toward learning how to find your way around. In time, knowing the
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Copyright © 2012 Skyhound. All rights reserved.
constellations will help you find the more distant wonders of the Universe
that your binoculars or telescope can reveal.
Once you can find you way around the sky you will be able to find bright
double stars. The next step is to hunt down your first real deep sky objects:
open star clusters. Open star clusters are fairly easy to find and make for a
pleasing view in your binoculars or telescope. SkyTools will be able to help
you pick out the clusters that are most appropriate for you.
Lastly, a note about those faint fuzzies: many people are happy observing
the moon, planets, and double stars. Moving on to the more difficult deep
sky objects (other than star clusters) will require a new kind of “looking.” A
deep sky object is a celestial object that is not a single star and lies beyond
our own solar system—beyond the family of the sun. These objects are
exotic by nature, but often disappointing to look at in the telescope. When
you look at the “Great Nebula” in Orion or the majestic Andromeda Galaxy in
a telescope they will appear as little more than fuzzy clouds against the
darker sky. In fact, most deep sky objects are faint and will typically show
little detail. So why look at them at all? It boils down to appreciating what
you are seeing; how amazing it is that you are seeing these things with your
very own eyes, and the hunt. In order to appreciate most deep sky objects
you need to look not only with your eyes, but with your mind as well. That
elongated fuzzy cloud takes on meaning when you try to imagine just how
big and how far away it is. People often say the Universe makes them feel
small. Yet for all its size and distance, we as human beings can know these
things. Our bodies are small, yet our minds can comprehend so much of the
Universe, if only we take the time to do so.
If you do manage to tease out a hint of detail, then you can consider that a
victory. For many deep sky observers there is also a great satisfaction that
comes from knowing that they can navigate their telescope to these objects.
Some astronomy organizations, such as the Astronomical League, have
awards and certificates for those who manage to hunt down all the objects
on one of their observing lists. The SkyTools Starter Edition has several of
these lists included that are suitable for smaller telescopes.
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What SkyTools can do for you
The SkyTools Starter Edition does two basic things: it helps you select
objects that are appropriate for your telescope or binoculars on a given night
and it helps you find them in the sky.
In the real world these two things are complicated. But it doesn’t need to be
complicated if you have help. There is a lot of expertise in astronomy built
into the program for you to take advantage of in order to make looking at
the sky simple.
There are three questions that SkyTools is designed to answer:
1. What can you see in your telescope from your backyard tonight?
2. When should you look at each object?
3. How do you find the object in the sky?
SkyTools Starter Edition consists primarily of the Nightly Planner, which is
what you see when you open the program, and the various Charts. The
planner helps you answer the first two questions above and the charts
answer the third.
Using the SkyTools Help System
SkyTools has an extensive help system built into the program. Every window
and dialog has a Help button. The associated help page is designed to
answer any questions you have about the window or dialog.
The main program window has three help buttons at the top. The Planner
Help button takes you straight to the help page for the Nightly Planner. The
How To… button opens the How To… section of the help system. If you know
what you want to do, but don’t remember how to do it, the How To… section
is the place to look for an answer. Finally, the Help Contents button will open
the help system with the table of contents displayed on the left. From there
you can navigate to any of the topics.
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Growing with the Hobby
SkyTools Starter Edition does just that—it gets you started with amateur
astronomy. In time you may want to move to a larger telescope, start
observing from a dark-sky site, or take up astronomical imaging. When you
are ready to move on SkyTools can grow with you. The SkyTools Standard
Edition is designed for more serious visual observing with larger telescopes.
The SkyTools Professional Edition offers the most advanced features and
supports astronomical imaging.
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Copyright © 2012 Skyhound. All rights reserved.
The Basics of Observing
Using your telescope or binoculars successfully requires some basic
knowledge and skill. This chapter outlines what you need to know to get
started in observing.
Equipment Basics
The tools of astronomy involve basic concepts and more than a few arcane
terms. This section serves as a simple introduction to the primary concepts
and terminology. Even though basic, this is the most technical part of this
handbook.
Binoculars
All binoculars are characterized by a simple numerical description, e.g. “7 x
50”. The first number is the magnification (power). The second number is
the aperture (diameter of each primary lens) in mm. Therefore your basic 7
x 50 binoculars have a magnification of 7 and an aperture of 50 mm.
Magnification x Aperture (mm)
Magnification is how much closer things will look. The aperture determines
how much light is gathered; the more light the fainter you can see.
What binoculars excel at is wide sweeping fields of many more stars than
you can see with the naked eye. So for astronomy the aperture is more
important. Larger aperture means that you will see fainter stars and more
objects in the sky. Greater magnification means a smaller field of view and
more difficulty holding the binoculars steady.
Telescopes
There are two basic types of telescopes. Refractors use a lens at the front
end of the tube where the light shines in. The light converges to a point at
the other end of the tube where we place an eyepiece to view it. Refracting
telescopes tend to have long tubes and you always look in the end of the
tube opposite where the light enters. The first telescopes, such as the one
Galileo used, were refractors, and when most people think of a telescope
they think of a refractor. Many telescopes made for beginners are refractors.
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Reflectors use a mirror instead of a lens. You can tell if a telescope is a
reflector by looking into the front end. If you see a mirror it is a reflector.
The light enters the front of the tube, which may be open, and then travels
down the tube to the back where the mirror is. The light is reflected back in
the direction it came from, converging to a point. If you were to place an
eyepiece at the point where the light converges your head would block the
light from entering the telescope! So a small secondary mirror is used. In a
Newtonian Reflector the mirror directs the light out through a hole in the
side of the tube to the eyepiece. You can spot a Newtonian Reflector
because the eyepiece is always on the side of the telescope near the front.
Dobsonian telescopes are a type of Newtonian reflector.
In a Cassegrain Reflector a small secondary mirror at the top of the tube
reflects the light back through a hole in the primary (or main) mirror. The
eyepiece is located at the back end of the telescope like a refractor. In
addition to seeing a mirror when you look into the front, you can spot these
telescopes by their short stubby tubes. These telescopes are half as long so
they make for a more compact design.
Most large amateur and professional telescopes are reflectors, due to the
lower cost in making a large mirror vs. a large lens and to the compact size
of the Cassegrain design.
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Astronomical telescopes are defined primarily by their aperture. The
aperture is the diameter of the primary lens or mirror. This is the most
important factor in any telescope used for astronomy because it determines
how faint you can see. When people talk about bigger telescopes they are
talking about larger apertures. Imagine a bucket set outside in the rain. The
wider the bucket the more rain it will collect. Similarly, the wider the
telescope the more light it will collect. This is why large-aperture telescopes
are sometimes called light buckets.
A larger aperture will translate to a fainter magnitude limit. The magnitude
of a star is a measure of how bright or faint it is. Brighter stars have smaller
magnitude numbers. A larger aperture allows you to see fainter stars with
larger magnitude numbers. Your eye can see stars down to about 6th
magnitude. Your binoculars may show stars to 10th magnitude and a
telescope may show stars to magnitude 13. The number of stars you can see
increases greatly with the magnitude, so the difference between a telescope
that can see stars as faint as 12th magnitude and one that can see as faint
as 13th can be quite dramatic.
Larger apertures will also reveal more detail of the moon and planets, but
with a caveat. Often the steadiness of the atmosphere will limit how much
detail you can see regardless of the size of the telescope. But on a steady
night a larger-aperture telescope will reveal detail that a small telescope
cannot.
The aperture of a telescope is usually specified in units of mm (sometimes
cm) or inches. A small telescope is generally one with an aperture of 5
inches (128 mm) or less. A large amateur telescope may have an aperture
of 10 or 12 inches (25 or 30 cm). Very large amateur telescopes may be 20
inches (50 cm) or more.
Another number you will see associated with telescopes is the focal length.
In simple terms the focal length of a telescope is how far the light travels
from the primary lens or mirror to the eyepiece. Telescopes with longer focal
lengths will offer higher magnification and a smaller field of view for the
same aperture and eyepiece. A telescope designed to give sweeping wide
fields of view will have a short focal length. A telescope designed for looking
at the detail in the moon or planets will have a long focal length. Most
telescopes are a compromise between the two and will perform both tasks
well.
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The focal length of a telescope is specified in the same units of measure as
the aperture. A 4-inch (aperture) telescope may have a focal length of 20
inches. A 120 mm telescope may have a focal length of 600 mm. Notice that
in both of these examples the focal length was 5 times the aperture. This is
another way to specify the focal length, called the focal ratio (or f/ratio).
These telescopes are both f/5. This is a short hand notation for the focal
ratio being 5 times the aperture.
A focal ratio of f/5 means: focal length = 5 X aperture
A telescope designed for sweeping wide field views might be f/4 while one
designed to look at the moon, double stars, or planets might be f/10.
Sometimes a telescope is described by its aperture and focal length. In other
cases it is described by the aperture and focal ratio. If you know the focal
ratio you can always calculate the focal length and vice versa.
Eyepieces and Barlow Lenses
The eyepiece you insert into your telescope determines two things: the
magnification (or power) of your telescope and the field of view. The
magnification is how close things will appear; higher magnifications allow
more detail (up to a point). The field of view is how much sky you see. A
larger field of view means that you see a wider swath of sky.
Eyepieces usually have a number marked on the side in mm. This is the
focal length of the eyepiece. Smaller numbers mean higher
magnification and smaller fields of view.
One of the biggest mistakes that new observers
make is to use too much magnification. Higher
magnifications make it more difficult to use your
telescope. Small movements of the telescope can put
objects right out of the field of view. Unless your
telescope tracks the sky, the rotation of the earth will
cause objects to quickly move out of the field of view.
It is also more difficult to focus and things will
generally look more blurry. Higher magnification may
not always mean more detail. Often your telescope or
the steadiness of the atmosphere will put a practical limit on how much
magnification you can use.
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Always start with your widest-field lowest-magnification eyepiece.
Once you have your object centered, move to ever-higher magnifications.
Find the eyepiece that gives you the most pleasing and comfortable field of
view for your target object.
A Barlow lens increases the magnification of a given eyepiece, usually by a
factor of two. Insert the eyepiece into the Barlow and then the Barlow into
the telescope. Some Barlow lenses are zoom-able, allowing you to change
the magnification on the fly.
The SkyTools Telescope Report
SkyTools can generate a report for your telescope that tells, among other
things, the actual magnifications and fields of view of your different
eyepieces, with and without a Barlow.
To generate a report click on the Add/Modify Telescope button on the
planner button bar. Select your telescope and then click Report.
Note the typical practical magnification limit. This is the maximum useful
magnification for your telescope. You should avoid using magnifications
higher than this value. For that matter, magnifications close to this value
will likely be unsatisfactory.
Also note the recommended eyepieces. The eyepiece focal lengths
recommended here provide a good range for your telescope. It is
assumed that you also use a Barlow lens in addition to eyepieces listed.
Compare these to the eyepieces you own at the bottom of the window.
You don’t need to match the recommendations exactly, but you should
have a similar range. If you are considering buying additional eyepieces
this information could be very useful.
Click on the field of view column to sort your eyepieces by the field of
view. If the largest field of view isn’t at the top, click on it again. It’s a
good idea to print this report so that you can refer to it later.
Some eyepieces are better than others. Seasoned observers will sometimes
spend almost as much on their eyepieces as they do on their telescope.
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Copyright © 2012 Skyhound. All rights reserved.
What they are often paying extra for is better eye relief and a wider
apparent field of view.
Eye relief is how far away from the eyepiece you can place your eye and still
see the full field of view. An eyepiece with a long eye relief will be much
more comfortable to look through.
Apparent Field of View is how wide the view through the telescope appears
to your eye. Two eyepieces may show the exact same piece of sky, but an
eyepiece with a small apparent field of view will place the sky into a small
circle, sort of like looking through a narrow paper tube. An eyepiece with a
wide apparent field of view will expand the circle. Think of it like sitting in a
movie theater. If you sit in the back row the screen is small; you have a
small apparent field of view. If you sit in the front row the screen fills your
view and you have to move your eye around to see everything. It’s still the
same movie (the actual field of view remains the same). When it comes to
eyepieces people find the wide expansive view to be much more pleasing. A
typical apparent field of view is 50o. Expensive eyepieces can enlarge that to
as much as 120o. Another advantage is that when using an eyepiece with a
wide apparent field of view objects don’t move out of your view as quickly
due to the rotation of the earth, which gives observers more time to look at
the target object when using a telescope that doesn’t track the motion of the
sky.
Mirror Diagonals
A mirror diagonal is a device that lies between your eyepiece and your
telescope. It sends the light at a right angle so that it is more comfortable to
look into your telescope. Your eyepiece inserts into it.
Most refractors and Cassegrain telescopes have a
mirror diagonal because you look into the back end.
Without the mirror diagonal you would have to get
very low to the ground and bend your neck to look up
into the sky. Most Newtonian telescopes don’t require
a mirror diagonal because you look into the side.
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Copyright © 2012 Skyhound. All rights reserved.
Telescope Mounts
Telescope mounts break down into two basic types: Equatorial and AltitudeAzimuth.
Alt-Azimuth mounted telescopes work like a gun turret; they move up and
down (altitude) and around the horizon (azimuth). The most common altazimuth mounts are simple tripods. Dobsonians also use and alt-azimuth
mount. In this case the telescope base sits on a turntable that rotates
around the horizon. Telescopes with alt-azimuth mounts don’t usually follow
objects in the sky as the earth rotates. Objects will continually move across
the field, particularly at high magnification, requiring constant nudging to
keep them centered. On the other hand, alt-azimuth mounts are light, easy
to set up, and easy to point around the sky.
Equatorial-mounted telescopes are aligned with the earth's axis of rotation
such that they only need to move in one direction to follow targets in the
sky. They usually have a clock drive motor that keeps objects centered in
the eyepiece for long periods of time. This can be a great advantage when
trying to carefully study an object at high power, take photographs, or show
other people things in your telescope.
Finding Devices
Telescopes only show a small part of the sky. This can make it difficult to
point them at what you want to look at. Finding devices help you point your
telescope; they attach to the outside of the telescope tube. There are two
basic types of finders.
Magnifying finders are like little telescopes; they have a lens and an
eyepiece. These finders have the advantage that they show more stars than
you can see with your naked eye, but they have the disadvantage of only
showing as small part of the sky. These finders may also rotate the view of
the sky similarly to the telescope, which can be confusing because the
telescope may move in the opposite direction you expect it to while looking
through the finder.
Non-magnifying finders mark where the telescope is pointing via some sort
of illuminated marker. You see the same stars that you would normally see
with your eyes, but a marker tells you where the telescope is pointing. Some
popular finders of this type are the Telrad, Rigel Quikfinder, and various reddot models. In some cases a bull’s-eye or cross-hair reticle appears on the
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Copyright © 2012 Skyhound. All rights reserved.
sky and in others a simple red dot marks the position where the telescope is
pointing. These finders have the advantage that they are easy and
comfortable to use, but they don’t show many stars to navigate by.
Setting-Up SkyTools
When you start SkyTools for the first time you will be prompted to enter
information about your location, binoculars and telescope. Once you enter at
least one of each type it will stop prompting when you start the program. If
you only use binoculars or only use a telescope, you can stop it from
prompting by clicking the I Don’t Use Binoculars or the I Don’t Use a
Telescope buttons.
SkyTools uses this information to help you plan observations and to make
finder charts. It is important that what you enter be as accurate as possible.
You can always edit your location or add additional locations by clicking on
the currently selected location at the top of the planner or finder chart.
Edit your telescope or add more telescopes by clicking on the Add/Modify
Scopes button on the button bar at the top of the planner.
Edit your binoculars or add more binoculars by clicking on the Add/Modify
Binoculars button on the button bar at the top of the planner.
Tip: look at the graphic at the top of the planner. If the middle of the dark
band isn’t near midnight then there is a problem with your location settings.
Check your longitude to make sure it has the correct sign (it should be
negative in the western hemisphere) as well as your time zone.
Magnitude of Faintest Star
This is a critical value for your observing location. It defines how much light
pollution there is at your location which in turn determines what you can see
and what you can’t. Light pollution is light that spills into the sky from your
own city or from those nearby. The lights make the sky bright in the same
way the sun and moon do, washing out your view of faint objects and even
making many faint objects unobservable. It is rather unfortunate because
most light pollution is completely unnecessary. Better lighting choices such
as simple shields to keep the light from spilling into the sky would make a
huge difference.
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You can estimate your sky brightness by selecting (Urban, Suburban, etc.)
when you add a new location. But this will be a crude estimate. You may be
able to see things that SkyTools think you can’t or SkyTools may think you
can see things that are not visible to you.
For the best accuracy I recommend directly measuring the faintest star you
can see overhead. This may be a bit advanced for those who aren’t yet
familiar with the sky or SkyTools. It may be a good idea to wait until you are
more familiar with both before measuring your sky brightness.
The Procedure for Measuring your Sky Brightness
1. Pick a night when the sky is clear and there is no moon.
2. Open a Naked Eye chart for a convenient time when the sky is going to
be completely dark on this same night. One way to do this is to rightclick on the NightBar (graphic at the top of the planner) with the
cursor above the time you have chosen.
3. Click on your observing location at the top of the chart. Select your
location from the list. Note the magnitude indicated under Magnitude
of Faintest Star. Add 0.5 magnitudes to this number. E.g. if it says 6.5
then add 0.5 to get 7.0. Click on the menu to the left and select Enter
Limit >>. Type your number to the right (7.0 in our example). Close
the dialog box.
4. Click on the blue “target name” hypertext in the top left corner of the
chart. Type Zenith into the Quick Search box and click Search. Click
Ok. The chart should now be targeted at the Zenith (directly
overhead).
5. Click the S button on the button bar to orient the chart toward the
south.
6. If you don’t see constellation lines on the screen press the “c” key to
toggle them on.
7. Click the Print button on the button bar at the top of the chart. Click
Print again on the dialog that appears.
8. Take the chart outside about fifteen minutes before the time you chose
(which will be marked on the chart). For best results, let your eyes
adjust to the dark for about a half hour.
9. Stand facing south and look overhead. Looking at just the bright stars
on both the chart and the sky, try to pick out the constellations
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Copyright © 2012 Skyhound. All rights reserved.
overhead. Keep in mind that in step 3 we intentionally made the chart
show fainter stars than you will probably be able to see in the sky.
10.
Once you have matched what you see in the sky to what you see
on the chart look for the faintest stars you can find in the sky and
mark them on the chart.
11.
Take the chart back inside to your computer. If you haven’t
opened any other charts, click the Open Last Chart button on the
planner button bar. Otherwise you will need to recreate your chart on
the screen by selecting the same time, targeting the Zenith, and
orientating it toward the south.
12.
Now find the stars you marked on the paper chart on your
computer screen. Pass your cursor over the stars you marked. The
star will be identified in the status area at the bottom left side of the
window. The last number will say something like, “V5.8”. That is the
magnitude of the star. In this way write down the magnitude for each
star you marked. Note the faintest star you marked, the one with the
highest magnitude number.
13.
Click on the observing location at the top of the chart. It should
still say Enter Limit >> under Magnitude of Faintest Star. If not, click
on it and select Enter Limit >>. Type the magnitude of the faintest
star you can see overhead on a dark night into the box on the right.
Click Ok.
From now on SkyTools will accurately take into account how bright the sky is
at your location.
Learning the Sky
The very first thing to do as an amateur astronomer is to get used to looking
up, not just when you are outside at night but all of the time. So many
people spend their lives under this amazing, ever-changing sky but never
stop to look.
Begin by noting the movement of the Sun. Where does it rise and set? Have
you ever wondered if it always rises and sets in the same spot on your
horizon? An interesting project is to make a drawing of your local horizon
and draw the position when it rises or sets every few days. You may be
surprised at the result! And how high does the Sun get in the sky near noon?
Does it always get that high or does it matter what time of year it is? If you
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take a trip, particularly to another latitude, how does that affect where the
Sun is in the sky?
Be on the lookout for the moon. Can you see the moon during the daytime?
When does it rise and set? Is it the same time every night? Watch how the
bright sunlit part changes a little every day. Books, movies, and even video
games often get the moon wrong. In no time you will start noticing their
mistakes.
Sunrise and Sunset
Going out at sunset can be particularly rewarding. Watch the path of the sun
as it sets; is it going straight down or at an angle? And when the moon is
above the sun in the West, notice the sunlit side. Is it on the side toward or
away from the sun? On the night of a full moon, when and where does the
moon rise? Where is the sun in relation? Can you see how the sunlit side of
the moon always tells you where the sun is?
If you see a very bright white star in the western sky after sunset, that may
be Venus. Wait for the sky to darken a bit and note its position relative to
other stars. Do this again on another evening. Does it move from night to
night?
You can use SkyTools to identify objects after sunset for you. Select the
night and your location at the top of the planner. The graphic at the top is
called the NightBar. It tells you how dark the sky will be during the night,
indicating sunset, sunrise, twilight and moonlight by the shading of the
background. Along the bottom of the graphic is your local time. Right click
with your mouse on the NightBar after sunset during twilight. Select Display
Naked-Eye Chart and then W for west.
The Naked-Eye chart will show you the western horizon at the time you
clicked. Planets will be displayed with their planet symbol and will be labeled
if you have their labels turned on in the View Controls. Set the time-step to
30 minutes and then click the time-step forward/back buttons to see how
the sky will change before or after sunset.
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Notice how everything in the west is following the sun down. The west is the
setting half of the sky. Everything on that side of the sky gets lower with
time. The eastern part of the sky is the rising half. If you want to look at
something low in the western sky don’t wait too long! Venus, Mercury, the
moon just after the New phase, and the occasional bright comet may be low
in the western sky during twilight. You will only have a short time to view
them before they get too low, so timing is critical.
Try setting the time-step to one day and preview how the sky will change
each night as you click the time-step forward button.
The twilight before sunrise is the opposite of sunset. Click on the SkyTools
icon on the Windows Taskbar to bring the planner on top. Right click on the
NightBar again, but this time click over on the right side during the dawn
twilight. As before, select Display Naked-Eye Chart, but this time choose E
for east. Venus may show up in the morning if it wasn’t there in the evening.
Try time-stepping ahead in 30-minute steps. Objects low on the eastern
horizon are rising higher in the sky so we can get a better look at them
(higher is always better) but soon the sun rises and washes everything out.
So the morning is also a race. In this case we want to see an object higher
in the sky but before the sun rises. Once again timing is critical.
Constellations – Recognizing Star Patterns
The one skill that every sky observer must master is recognizing star
patterns. It doesn’t matter if you are casually observing the change of
seasons in the naked-eye sky, using a finder chart to point your telescope,
spotting a small or faint object in the eyepiece of your GOTO scope, or
positioning your professional imaging system via pictures on a computer
monitor--it’s exactly the same skill.
A great way to learn this skill, while at the same time learning your way
around the sky, is to learn the constellations. Most people already know a
few constellations, although they may be surprised that some of the
constellations they think they know, such as the Big Dipper (or Plough), and
Little Dipper, aren’t truly constellations at all. Others, familiar with the signs
of the zodiac, will be surprised to discover that there are nearly 90
constellations! There are also some differences in nomenclature. For
instance, the zodiacal sign Scorpio is the constellation Scorpius. That’s
something to keep in mind if you don’t want to get funny looks after joining
your local astronomy club!
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To a sky watcher a constellation is a pattern of stars in the sky. The
mythology of the ancients and the figures that people have imagined to fit
the star patterns can be a fascinating subject. But that is beyond our scope
here. For our purposes we will not attempt fancy reconstructions of
imaginative people of the past, but rather focus on the star patterns
themselves. For this reason SkyTools uses a minimalistic approach for
drawing the constellation “stick figures.” There is no standard for the
constellation patterns so you will see them drawn in many different ways.
The SkyTools patterns are drawn with an emphasis on marking the
memorable star patterns in the sky. Little effort is made to force them to
adhere to the mythological figures they represent. This will make recognizing
these patterns in the sky easier.
Which constellations you can see depends on what your latitude is.
Northern-hemisphere observers see constellations in the northern part of the
sky that southern-hemisphere observers can’t, and vice versa. The
constellations near the celestial equator (or along the Ecliptic where the
zodiacal constellations reside) can usually be seen from either hemisphere.
The time of year also determines which constellations you can see in the
evening. If you go out after sunset each month, old constellations will
disappear in the west and new ones will rise in the east. This is why we refer
to constellations by season, such as winter or summer constellations. But if
you stay up late enough, or get up before sunrise, you will see the winter
constellations in the summer and vice versa. That is because as the night
goes on the constellations of the early evening will set in the west and new
ones will rise in the east.
Let’s get down to it and learn some constellations.
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Open SkyTools and select the date and your observing location at the
top of the planner.
Select Naked Eye as your “telescope”.
Select The Constellations observing list.
Select Objects at or near their best
Select Detectable
Check the box next to Sort in best observing order.
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These settings will show you the constellations that are bright enough to
that you can make out the primary star patterns and that are in a good
position to be observed.
Click on the right-most red vertical line on the NightBar graphic at the top of
the window. Holding the mouse button down, drag this time slider until it is
near 10 PM (22:00). This will limit the constellations in the list to only those
that are good to look at before 10 PM.
Pick a constellation from the list. I recommend one of the following
constellations because they are fairly prominent: Orion, Cassiopeia, Cygnus,
Lyra, Leo, Ursa Major (aka the Big Dipper or Plough), Bootes, Scorpius, or
Crux. Right click on your constellation and select View Naked Eye. The
Naked Eye chart will appear. If the constellation lines (stick figures) are not
visible, press the “c” key. This will make them appear.
If the constellation labels are not visible, press the “l” key. If they are still
not labeled, open the View Controls dialog via the button on the button bar,
select the Labels tab, check the box next to Constellations, then close the
dialog.
The constellation you selected when you opened the chart (your target
constellation) will be highlighted with thicker lines than the others. It will
also be near the center of the chart.
The constellation Orion on a printed chart (left) and in the sky (right).
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Let’s try an experiment. Press the “c” key again to turn off the constellation
lines. Then press the “l” key to turn off all the labels. Can you still spot the
constellation? Try pressing the “c” key repeatedly; note which stars are
connected with lines and then try to memorize the actual pattern of stars
without the lines. After all, there are no lines in the night sky! Don’t try to
memorize every star, just the brightest ones.
Try picking out the one, two or three brightest stars in the constellation
(largest dots on the chart). Concentrate on seeing the relationship these
stars have to one another with the lines turned off. Do they make a
memorable pattern of some kind? Three stars in a row? An interesting
triangle? Or maybe one of the stars is the brightest star on that side of the
sky. These are all things that are going to stand out in the real sky as well.
Print this chart to take outside with you. Print out a second chart with the
lines and labels turned off. Take both charts out with you near the time
indicated on the charts.
To successfully find your constellation it is important to know where north,
south, east and west are along the horizon at your observing location.
People often think they know where north is, but in practice they are
surprised how far off they are. It is a good idea to borrow a compass or GPS,
or use Google Earth to determine how north relates to a nearby street.
Once you know where north is, south is easy (in the opposite direction). The
Overhead Sky Chart can be useful to orient yourself with respect to the sky.
Select your constellation in the planner as you did before but this time when
you right-click on it, select View Overhead Sky. As before, press “c” to
display the constellation lines and “l” to show the constellation labels.
Print this chart to take outside with you as well. Again, use it near the time
printed on the chart. Turn facing south. Hold the paper chart up over your
head. South will be at the bottom, east will be on your left, and west will be
on your right. Use a red flashlight to read the chart.
You may be able to find your constellation from the Overhead Sky Chart,
and with time it will help you find constellations all over the sky. But for now
use the Naked Eye charts we printed out instead.
Stand looking in the direction indicated on the Naked Eye chart. Using the
chart with lines as a guide, find the brightest stars in your constellation on
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the chart without the lines. Pick out the brightest few stars and note their
relationship to each other. Turn to the sky, and keeping in mind that
everything in the sky will be bigger and more spread out, look for the
brighter stars in the sky in that direction. Can you spot the bright stars that
have a similar relationship to one another as on the chart? When you do, use
your chart to determine where the rest of the stars in the constellation are
using the bright stars you already identified as your starting point.
Once you have identified your constellation in the sky, put away the charts
and have a good long look at it. Forget all about the charts and any
mythology and what you may have read that somebody else sees when they
look at this constellation. What matters is only what you see before you.
Feel free to interpret and remember the star patterns in any way you want.
There is no right or wrong way. Remember, what matters is that you can
pick out this particular pattern of stars, and the surrounding area of sky,
again and again.
Go out on subsequent nights and find your constellation again, without any
charts. Just keep in mind that it won’t always be in the same part of the sky
at different times of night or at different times of the year. Soon you will
always be able to recognize your constellation and you will have made a
lifelong friend in the sky.
Once you can recognize a few constellations you can use them as signposts
to find others. A good example is finding Polaris after you know where Ursa
Major (the Big Dipper or Plough) is. Polaris is also known as the North Star.
Many people think Polaris is the brightest star in the sky, but in fact it isn’t
all that bright. Polaris does mark the brightest star in the faint constellation
of Ursa Minor, but what makes it important is that it marks north for
northern hemisphere observers.
To find Polaris draw an imaginary line between the two stars at the “dipper”
end of Ursa Major and extend it toward the north (around your horizon). At
a distance of about 5 times the separation between these two stars you will
come across a lone star. This is Polaris. Polaris marks the end of the handle
of the “Little Dipper” so extending away from it will be the rest of the
constellation Ursa Minor.
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You don’t have to use pre-fabricated methods to find nearby constellations in
this way. Feel free to make up your own pointer stars or use triangles that
you find on the chart to locate nearby constellations in the sky.
Observation Planning
You could just take your telescope or binoculars outside and start looking at
anything that strikes your fancy, and in fact this is a fun way to get started.
But you will soon run out of bright stars or clusters to point your telescope at
and begin to wonder what you may be missing.
You can also use a guide book to suggest things to look at, like the one
presented in later chapters of this book. The guide book may even have
charts to help you navigate to the suggested targets in the sky. But what a
guide book can’t do for you is tell you which targets you should look at on
any given night and what time of the night you will get the best view. That’s
where observation planning comes in. No guide book can know your latitude,
local light pollution, the phase of the moon, or details about your telescope—
things that matter greatly. But once you tell SkyTools about them it can use
that information to suggest target objects tailor made just for you.
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Seeing objects at their best is complicated, but the basic idea is simple: in
general you want to observe them when they are high in the sky and the sky
is dark.
For some very bright objects like the Sun, Moon and Jupiter, the darkness of
the sky isn’t a big deal. Instead we try to observe them when they are high.
Similarly, a bright star cluster or small bright planetary nebula may not be
that affected by moonlight. But a faint galaxy may be invisible in your
telescope unless the moon is below the horizon. SkyTools can take all these
different factors into account, suggesting the best objects to observe on any
given night.
Your location will likely have some light pollution from the lights of your
community. It is critical to correctly set the amount of light pollution for your
observing location in SkyTools to accurately predict the visibility of fainter
objects. See Setting-Up SkyTools for how to do this.
There isn’t much you can do about light pollution washing out your sky other
than take your telescope some place far away from the lights of cities. But
you can schedule around the presence of the Moon, which also washes out
the sky depending on its phase. A night when the moon is full is not a good
night to look at faint galaxies. For that matter, even the moon isn’t a great
target then. It is better to concentrate on planets or double stars on such
nights. Once per month the moon nears its New phase and it will be dark all
night long. These are the nights you want to set aside to look at your faint
galaxies and nebulas.
I have found that astronomers and farmers always have something they can
talk about: the weather. The weather is critical to both. An astronomer of
course wants a clear dry sky. There are days when the blue of the daylight
sky takes on a special color and seasoned observers will know that it is
going to be a good transparent night. A transparent sky is one that allows
more light through to us. It is maddening that the light from distant objects
comes all this way only to get messed up at the very last instant by our
atmosphere. Anyone can tell that cloud cover will make observing useless,
but it takes experience to tell the difference between a clear sky and an
exceptionally transparent sky. On some nights faint objects will simply be
brighter and there will be more contrast, giving a more pleasing view and
making things easier to see. If you can see the Milky Way it will stand out
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much better. These are the nights that astronomers who like deep sky
observing live for. In time you will learn how to spot such nights.
Equally important to the astronomer is how steady the air is. The term for
this is seeing. Some people use “seeing” as a general purpose term to
describe a good night of observing, but in fact it has a very precise technical
meaning. There are even seeing scales used to compare how steady the air
is from night to night.
When you look at a bright star, particularly near the horizon, it will usually
twinkle. Twinkling stars may make for cute nursery rhymes, but they are a
bad sign for astronomy. If the air was perfectly steady the light would pass
through unaffected.
Have you ever seen heat rising off a road in the summer? You can see things
shimmer in the distance. This is because the air is at different temperatures.
As the light passes from hot air to cold or vice versa it is bent a little, like in
a lens. If the air is moving the amount of bending will even change as you
watch. This is why stars twinkle. When you look at a twinkling star in your
telescope it will magnify the effect. On nights of poor seeing a bright star will
appear as a bouncing blob of light rather than a sharp point. If you try to
look at the moon or a planet on such a night it will look blurry. So keep an
eye out for nights when the stars don’t twinkle as much. These nights will
give you sharper views. Another thing to watch for is how the seeing
changes over the course of a typical night. It is common for the twinkling to
be worse just after sunset than later on. Don’t count a night out until the air
has had the chance to settle down.
The more air you look through the better chance it has to make your view
blurry. When we look directly overhead the light from the star takes its
shortest path through the air. As you look closer to the horizon you look
through more and more air. In fact, by the time you get 2/3 the way down
to the horizon, at an altitude of about 30 degrees, you are looking through
twice as much air as overhead. Obviously then it is important to look at
objects when they are higher in the sky. You will notice that even though a
star near the horizon is twinkling madly, a star higher overhead may be
steady. SkyTools takes the altitude of an object into consideration, always
trying to get you the best possible view.
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Using the Nightly Planner
When you start SkyTools it opens with the planner, the idea being that you
don’t need a chart until you know what you want to look at. The planner is
designed around the idea of an Observing List. This is a list of objects that
you may wish to observe. SkyTools has a variety of observing lists with
objects suitable for binoculars and small telescopes. You can also make your
own observing lists via the Designation Search Tool opened via a button on
the button bar. If you know the names (or designations) of objects you want
to observe, say from a magazine article, then you can type them in here.
SkyTools will look them up in the database and then you can add each
object to any observing list, even a new list you create for yourself.
Another way to create an observing list is the Nightly Observing List
Generator, which is also opened with a button on the button bar. This tool
will automatically create a list of objects preselected for the date, location,
and telescope or binoculars that you have selected on the planner.
The next step is to select an observing list, choose a night, your location,
and your telescope or binoculars at the top of the planner. The current
settings are indicated in blue hypertext. Simply click on them to change
them. It is probably best to open the program and follow along with the rest
of the instructions here.
The graphic at the top is called the NightBar. This shows an entire 24-hour
period from noon on the date selected to noon the next day, with midnight
in the middle. The time of day is marked along the bottom. How dark the
sky is at any time is shaded in the background.
The altitude of the sun is indicated as a yellow dashed line. When at the top
the Sun is overhead. The bottom of the graphic is the horizon. Note that the
direction in the sky isn’t indicated, just the altitude of the object above the
horizon over time. Similarly the altitude of the moon is indicated by a teal
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dashed line. Take some time to familiarize yourself with the NightBar
because it conveys a lot of useful information very quickly and simply.
If you select an object in your observing list a red-dashed line will appear on
the NightBar. The red line shows the altitude of the object you clicked on.
You could plan when to observe this object by simply looking at this line.
Remember, the name of the game is to look at most objects when they are
high in a dark sky. If the red dashed line is only high in the sky during
daylight then this isn’t a good night to look at it. If the red dashed line
doesn’t appear at all, then you may not ever be able to see this object from
your latitude. If the red line is high at 10 PM (22:00) but the moon is also
up, turning the background gray, then this may also be a poor night to look
at the object, particularly if it is faint.
Notice the horizontal green line running across the width of the NightBar.
This is the altitude at which you are looking through twice as much air as
overhead (astronomers call this 2 Airmass). What we are usually looking for
is a red-dashed line that rises above the horizontal green line when the
background is dark.
Hover your mouse pointer over the NightBar and let it sit there for a
moment. A fly-up will appear that gives a useful summary of the night,
including the phase of the moon.
The next thing to do is to get rid of all the objects in our observing list that
aren’t going to be good to look at tonight. SkyTools can do this automatically
via filters. There are two filters: quality and difficulty.
The quality filter looks at how good the view of each object is compared to a
perfect night: is it high in the sky? Is it in darkness? The quality of our
opportunity to look at an object on this night is pre-computed. You can see
what was calculated for each object by looking in the quality column. The
top of this column has a stoplight. The quality is indicated by the color of the
light: green when an object is at its best, yellow when near its best, and red
when the quality is low.
What we typically want to do is get rid of all the objects with a red status
light. We will observe those on a better night. To do this select Objects at or
near their best from the pull-down under where it says Filters. We could also
select Objects at their best only to further narrow down the list by removing
those with yellow status lights as well.
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Copyright © 2012 Skyhound. All rights reserved.
The difficulty to see each object in the selected telescope or binoculars is
also pre-computed. This is computed at the best time to see each object on
this night and takes into account all the changing factors, such as moonlight,
in addition to your location and telescope. Keep in mind that an object
marked as Challenging one night may be Easy on another. Difficulty can be
one of:
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Obvious
Easy
Detectable
Difficult
Challenging
Very Challenging
Not Visible
When marked as Detectable you should be able to see the object without
difficulty. Beginners should probably avoid Difficult and Challenging objects.
Very Challenging objects are those that you probably can’t see at all, unless
you are very experienced and the sky conditions are perfect.
What we typically want to do is to remove all those objects that aren’t at
least Detectable. To do this select Detectable from the difficulty pull-down
under Filters. You may want to limit objects to Easy or even Obvious to
further narrow your list.
You should now have a list of objects that are good to look at on the night
you picked. If you don’t see any objects the moon may be full; try another
night or select a more appropriate observing list such as Sun, Moon, and
Planets. It may also be that your conditions and telescope aren’t quite up to
seeing the objects in the list because they are too faint.
But what if you don’t want to be up all night? How can we get rid of those
objects that are only good to look at long after you are asleep? On the right
side of the NightBar you will see a red vertical line, or time slider. Place your
mouse pointer over the line and the pointer will change to a left/right arrow.
Depress the left mouse button. Holding the button down, drag the red line to
the left until it sits over the time you want to go to bed. Any objects that
don’t meet our filter criteria before you go to bed will be removed from the
list.
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Important note: the time sliders don’t change the optimum time to
observe each object nor do they change the difficulty or quality status, which
is computed at the optimum time. If the optimum time is 3:00 AM that is
still the best time to look, regardless of when you go to bed. That said, the
time sliders will filter out objects based on how they appear during the time
period you specify.
There is another red bar on the left that you can drag to remove objects that
aren’t at their best prior to the time you drag it to. Use this to isolate objects
that will be visible prior to sunrise if you plan to rise early or to set a time
period during the night.
You can reset all of these filters by selecting Reset Filters from the blue
Observing list menu.
Finally, check the box next to Sort in best observing order to sort the objects
in the order to observe them. This function starts by ordering objects by
their optimum time, but places some objects before others based on
whether or not they are rising or setting. Objects with the same optimum
time are grouped by constellation so you don’t move your telescope all over
the sky.
Now let’s turn our attention to the columns of the observing list. The
leftmost column is the object class icon, which tells you what type of object
it is. Planets, for instance, have a little Saturn icon, galaxies have a little
galaxy, etc.
Most objects have more than one name (or designation). The Primary ID
column lists the most commonly used name. The second most commonly
used name appears in the Alternate ID column. For instance, the Crab
Nebula is also M 1, so the Primary ID is the Crab Nebula and M 1 appears as
the Alternate ID.
Con lists the constellation the object is in using the standard three-letter
constellation abbreviation. These are listed in the Astronomy Nuts and Bolts
section.
RA 2000 and Dec 2000 are the position of the object in standard equatorial
coordinates. RA stands for Right Ascension and Dec stands for Declination.
The 2000 indicates that the coordinates are for the standard year 2000
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rather than the date selected. This allows for easy comparison to other
sources. See the Astronomy Nuts and Bolts section for details.
Mag stands for Magnitude and indicates how bright the object is. Lower
magnitude numbers are brighter, higher numbers are fainter. See the
Astronomy Nuts and Bolts section for details.
Size indicates the apparent size of the object in the sky. Units are o
(degrees), ’ (arc minutes) or ’’ (arc seconds). Again, see the Astronomy Nuts
and Bolts section for details.
Begin, Best, and End mark the period in time during which the object is best
observed on this night. Try to observe each object between the Begin and
End times. For the very best view, look at the Best time.
Difficulty is how difficult it is to see the object in the selected telescope or
binoculars on this night.
The last column, with the stoplight icon, is the quality of the opportunity to
observe each object on this night. Green means it is at its best, yellow
means near its best and red means this is a poor opportunity. It is better to
look at objects with green or yellow icons.
Double click on an object to see the Object Information window. This window
will display information about the object from the SkyTools database plus an
observing synopsis.
Right click on an object to open a chart on the screen or send a chart to the
printer, with the selected object as the target.
You can print multiple finder charts all at once using the multiple selection
(red check mark) column. First select the objects you want to make charts
for by clicking in the check mark column. Place a red check mark next to
each one. Then right-click in the check mark column and select Print chart
for each checked entry from the popup menu. Select the telescope or
binoculars you want to print finder charts for. Each object will be depicted at
the best time to observe it.
Tip: you can select more than one object at a time by holding the shift key
down and clicking on a range of objects. You can clear or select all the
objects at once by right-clicking on the check mark column heading. The
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Check Displayed option can be particularly useful for when you wish to check
all of the objects not filtered from the list.
Finding Targets in Binoculars
Every time you add a pair of binoculars to SkyTools a custom finder chart is
created just for them. You can customize each individual finder chart to fit
the way that you use each pair of binoculars.
In the previous section we learned how to display or print finder charts from
the planner. In this section we will see how to use them to find objects with
your binoculars.
The SkyTools finder charts make finding objects relatively easy. Start by
picking an easy or obvious object from the Starter Objects observing list. A
bright planet is a good choice. The planner will help you to select a good
object for tonight. Enter the date, location, and the binoculars you are going
to use. Follow the procedure outlined in the Bread and Butter of Backyard
Astronomy chapter for the type of target you are interested in. Once you
have selected a suitable target, right-click on it and select View “your
binoculars”. This will open the finder chart on the screen.
The binocular finder charts have two views; the Naked Eye View shows the
part of the sky where your target is, as seen to the naked eye. The Eyepiece
View shows the target object as seen in your binoculars. The target is always
at the center of the Eyepiece View. A circle represents the part of the sky
that you see when you look through the binoculars.
Click the Print button on the button bar to print the chart. The finder chart
will have the name of your target object on it. Because the sky moves during
the night, your chart was made for a particular moment in time, indicated at
the bottom. This is the Best time to observe the object as taken from the
Observing List because you opened the chart by right-clicking on the object
there. Take the chart out along with your binoculars near this time.
Try to find a spot where you can see the sky but there aren’t any bright
lights shining on you. The most difficult thing about binoculars is holding
them steady—that, and keeping your arms from getting tired. Look for
something you can steady yourself on. The roof of a car can work for targets
that aren’t overhead. If your binoculars have a tripod mount or bracket, use
a camera tripod.
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Find a bright star in the sky. While holding your gaze on the star, bring the
binoculars up to your eyes. When you see the sky in the binoculars you
should see the bright star. Adjust the focus on the star so that it is as tiny
and sharp as you can make it.
Now take out your finder chart. Use a dim red flashlight to limit the effect of
the light on your dark adaption. If you don’t have a red flashlight, tape some
red cellophane or red paper over the end of your flashlight.
Look at the Naked Eye View first. Locate the general direction in the sky and
the constellations that are marked. Start by noting the brightest star (or
planet) on the chart. Then find the brightest star you can see in that part of
the sky. Verify that you found the right star by noting any nearby stars on
the chart, e.g. perhaps a pair of stars down and to the left of your star. Are
those two stars also down and to the left of the star in the sky? If so, you
are on the right track.
Note the position of your target object, indicated by cross hairs on the chart.
Looking at the chart, get a feel for the location of the target. It’s all right if
the target isn’t visible to your eye and in an area devoid of stars. Locate the
nearest stars to the target, first on the chart and then in the sky. Now
estimate about how far the target is between two or more stars on the chart.
Perhaps it is about ¾ the way from the bright red star to the fainter star way
off to the right. Find that same spot in the sky, about ¾ the way between
these two stars. As you did before, hold your gaze on this spot and bring the
binoculars up to your eyes. When you can see the sky in the binoculars you
should be looking at the target object.
If the target isn’t obvious or you think you may not be looking in exactly the
right spot, note any bright stars you see in the binoculars and the geometric
patterns they make with the surrounding stars. Refer to the Eyepiece View
of the chart. Identify the brighter stars in the area and look for the same
geometric patterns. If you aren’t quite looking in the right spot in the
binoculars you may need to refer to stars surrounding the binocular view
circle on the chart. Once you identify where you are looking in the binoculars
you should be able to locate the target object. Again, refer to the Eyepiece
View of the chart to give you some idea what the target should look like, and
in particular, how large it should appear.
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You can also use an alternative approach, which may be more appropriate if
you aren’t holding the binoculars in your hands. Start as before by
identifying the surrounding stars and estimating where to look between
them for the target. But this time, start by pointing the binoculars at the
brightest nearby star. Once you find this star in the binoculars, sweep in the
direction of the target until it comes into view.
There are various products available for holding your binoculars steady, from
simple tripods to special binocular observing chairs that you sit in to
comfortably view the sky. For those handy with wood, there are plans
available on the web for making your own counter-weighted binocular
mount. These mounts have the particular advantage that their height can be
adjusted so that people of different heights can look through them, yet they
remain pointed at the target object.
Finding Targets at the Telescope
Every time you add a telescope to SkyTools a custom finder chart is created
just for that telescope. You can then customize each one to fit the way that
you use it.
Telescopes with GOTO and Digital Settings Circles
If you have a GOTO or DSC telescope that can be directed to targets in
the sky automatically, you should print the observing list and take it into
the field with you. Sort the list in the best order to observe before you
print it. Then observe each object between the Start and End times listed.
You may still wish to display or print finder charts to help you locate
objects in the eyepiece. In this case it may be useful to disable the naked
eye or finder views. The eyepiece view will be the most useful to you. Be
sure to select your lowest-magnification eyepiece at the top of the chart
and then insert this eyepiece when looking for things in the telescope. If
your telescope doesn’t always put the target in the field we recommend
that you zoom the eyepiece view of the chart out so that plenty of sky
around the eyepiece view circle is visible.
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In a previous section we learned how to display or print finder charts from
the planner. In this section we will see how to use them to find objects at
the telescope.
Traditional Star Hopping
Most people with small telescopes find objects in the sky by star hopping.
Traditional star hopping is the most difficult thing for beginners to master
and it can take a lot of time to find objects this way even for those who are
experienced. In traditional star hopping you start at a bright star and then
move the telescope from star to star, as seen in the finder or telescope, until
you arrive at the target. Each move is one hop. Sometimes people place
circles on their charts that represent the size of the finder or telescope’s field
of view at each hop. All this can be very tedious and time consuming.
Star hopping was invented for use with paper star atlases. Paper atlases
don’t usually show the faint stars that you can see in your telescope and the
orientation of the atlas doesn’t usually match what you see in the telescope
or finder. The patterns you see in the eyepiece may include stars that aren’t
on the atlas and the atlas is often rotated or flipped. This makes star
hopping quite difficult. Fortunately SkyTools offers an easier alternative.
Using the SkyTools Finder Charts
The SkyTools finder charts make finding objects relatively easy. These charts
use the Context Method. Rather than move the telescope from one place to
another we instead try to point it as close to the target as possible right
from the beginning. As in star hopping we do this in steps, but rather than
hop from place to place we move from the naked eye to the finder and
finally to the eyepiece. With each step we refine the position that the
telescope is pointing at.
Start by picking a relatively easy object from the Starter Objects observing
list. A bright planet is a good choice. Use the planner to select a good object
for tonight. Enter the date, location, and the telescope you are going to use.
Follow the procedure outlined in the Bread and Butter of Astronomy chapter
for the type of target you are interested in. Once you have selected a
suitable target right click on it and select View “your telescope.” This will
open the finder chart on the screen.
We’ll get to the details later, but in general the way you use this chart is to
start with the Naked Eye View. This will help you locate the right part of the
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sky as seen to your eyes. We point the telescope in this general area. Then
we move to the Finder View, using the chart to refine the position of the
telescope in the sky. Finally we use the Eyepiece View to locate the target in
the telescope, if necessary.
Customizing the Finder Chart
Before we go out into the field we should customize the finder chart a bit.
The most important chart view for finding objects is the Finder View.
Normally this view is the largest view (on the right). If not, hold the shift key
down and click in the finder view, dragging it into the view on the right. This
will switch the positions of the two views.
Be sure that you have your widest-field eyepiece selected at the top of the
chart. This will be your best eyepiece for finding things. The widest field
eyepiece will usually be the one with the largest number in mm. In other
words, of you have a 35 mm and a 12 mm eyepiece, select the 35 mm.
Make sure that there is no check next to the Barlow selection at the bottom
of the eyepiece menu.
The eyepiece view will have a circle on it that represents what you can see
when you look in the telescope. The target object will always be at the
center of the eyepiece view. You want the eyepiece view to show the detail
in the eyepiece circle, plus just enough of the surrounding sky so that you
can identify stars in the surrounding field should you not be pointing in
exactly the right place. To adjust how much sky you see around the
eyepiece circle, click in the eyepiece view and then click on the Zoom In or
Zoom Out buttons on the button bar.
Next we want to carefully adjust how much sky the Finder View is displaying.
Again, the target object will always be at the center of the Finder View. If
your telescope has a non-magnifying finder, zoom the Finder View in more
than the naked eye view. The naked eye view will then serve as a wide view,
showing constellations to navigate by, while the Finder View will show a
smaller part of the sky centered on where you want to point your telescope.
Don’t zoom in too far in though; you still need to see lots of stars to
navigate by. If you have a bullseye finder such as a Telrad you should see a
set of circles around the target that represent what you see when you look
through the finder. Similarly you may see some sort of reticule. If you use a
red dot finder the target cross hairs will serve to mark the position of the
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target. If you don’t see the target cross hairs click in the view and press the
“t” key to toggle them on.
If your telescope has a magnifying finder it will have a small circle that
represents what you see when you look through the finder. You want to
zoom the view in far enough that you can see a lot of detail within the field
of view circle, but at the same time you should leave lots of sky visible
surrounding the circle.
The Naked-Eye View should show enough sky that you can find
constellations to navigate by. If you don’t see any constellation lines, click in
the Naked Eye View and press the “c” key to turn them on. In this view the
target will be centered left and right, but it may be above or below the exact
center of the chart. This is so the horizon can be included to help you
navigate by. The target should be indicated by the target cross hairs; if not,
click in the view and press the “t” key to toggle it on. A box will indicate the
size and position of the Finder View for reference.
It can also be helpful for the compass points to be labeled along the horizon
of the view so you know which direction to look in. If you don’t see any
direction labels along the horizon right-click in the Naked Eye View and
select View Controls. Select the Labels tab. Ensure that the boxes next to All
Labels On/Off and Reference Points are checked.
On the following pages are examples of printed finder charts for telescopes.
The first chart was made for a magnifying finder. The second for a nonmagnifying finder (Telrad).
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In the Field
Once you have your finder chart set up as you like, click the Print button on
the button bar. The finder chart will have the name of your target object on
it. Because the sky moves during the night your chart was made for a
particular moment in time, indicated at the bottom. This is the Best time to
observe the object as taken from the observing list because you opened the
chart by right-clicking on the object there. Take the chart out to your
telescope near this time.
If you haven’t already done so, familiarize yourself with your telescope
controls in the daytime. Point the telescope at something in the distance and
then adjust your finding device so that it is pointing exactly where the
telescope is pointing.
If you keep your telescope indoors, take it outside well before you plan to
use it so that it can adjust to the outside temperatures. This will allow it to
perform better.
Select a spot for your telescope that has a good view of the sky but is
shielded as much as possible from any nearby lights. If you have a light
shining on your telescope you will not be able to look at anything but the
moon, bright stars, or planets. The glare from the light will not only make it
difficult to see the sky but it will keep your eyes from becoming dark
adapted which will make it impossible to see faint things in the telescope.
Serious deep sky observers who want to see faint objects keep light away
from their eyes for at least a half hour before they observe. This allows their
eyes to adjust to the dark. Even a brief exposure to light will reset your
night vision. If you have a bright light shining on your telescope you may
want to see about getting it turned off.
Once outside at night point your telescope at a bright star. Always start with
your widest-field eyepiece—the same one you selected for use on the finder
charts. Verify that the finding device and the telescope are both pointing in
the same place. If not, adjust your finder. Adjust the focus on the star so
that it is as tiny and sharp as you can make it.
Step 1: Start With the Naked Eye
Now take out your finder chart. Use a dim red flashlight to limit the effect of
the light on your dark adaption. If you don’t have a red flashlight, tape some
red cellophane or red paper over the end of your flashlight.
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Look at the Naked Eye View first. Locate the general direction in the sky and
the constellations that are marked. Start by noting the brightest star (or
planet) on the chart. Then find the brightest star you can see in that part of
the sky. Verify that you found the right star by noting any nearby stars on
the chart, E.g. a pair of stars down and to the left of your star. Are those
two stars also down and to the left of the star in the sky? If so, you are on
the right track.
Note the position of your target object, indicated by cross hairs. Once you
have a feel for where it is in relation to the bright stars, swing your
telescope in this general direction.
What happens next depends on the type of finding device you use. A nonmagnifying finder is a sort of sight that you look through. What you see is
the same as what you see without the finder, but the position of the
telescope is marked. A magnifying finder is like a little telescope.
Step 2: if Your Telescope has a Non-Magnifying Finder
Using the Naked Eye View of the chart, pick out the general area in the sky
where the target is. Next refer to the Finder View for a more close-up
depiction of this part of the sky. Pick out the spot where the target is on the
chart, relative to nearby stars. It is ok if the target spot is way out in the
middle of nowhere, where there aren’t any visible stars. In that case find the
nearest stars to the target, first on the chart then in the sky. Now estimate
about how far the target is between two or more stars on the chart. Perhaps
it is about ¾ the way from the bright red star to the fainter star way off to
the right. Move your head near the finder, keeping your eye on the target
area. Now look through the finder. In our example you would find the bright
star and then the fainter star off to the right. Aim the telescope at a point in
the sky about ¾ the way from the bright star to the faint one.
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Go ahead and point the non-magnifying finder (red circles) where there are no stars.
Now move on to Step 3 below.
Step 2: if Your Telescope has a Magnifying Finder
If you have a magnifying finder it may be useful to sight down the telescope
tube or along the tube of your finder to help point your telescope near the
right spot in the sky.
Once you think it is pointed close to where the target object is, look through
the finder. How much sky you see will depend on the finder. Hopefully you
will see enough sky that you will be able to make out a few stars.
Note any stars in the field and the geometric patterns they make. Refer to
the Finder View for a depiction of this part of the sky as seen in your finder.
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Your finder may rotate the view such that left and right are reversed and
everything is upside down. The Finder View on the chart should match what
you seen through the finder. There may be some rotation of the view
depending on the orientation of your head or telescope. You may want to
rotate the paper a little until it matches what you see.
Look on the chart for the same pattern of stars that you see in the finder.
The stars may be in the finder view circle or they may be off to one side.
Once you think you know where the finder is pointing, verify your position
by a simple test. Identify a star near your pattern in the Finder View of the
chart and then look for this same star in the finder. Is it there? If so then
you can be confident that you know where the telescope is pointing.
Using the Finder View, pick out the spot where the target is in the sky
relative to the stars that are visible in the finder. It is ok if the target is
where there aren’t any visible stars. In that case find the nearest stars to
the target, first on the chart then in the sky. Now estimate about how far the
target is between two or more stars on the chart. Perhaps it is about ¾ the
way from the bright red star to the fainter star way off to the right. Now look
through the finder. In our example you would find the bright star and then
the fainter star off to the right. Aim the telescope at a point in the sky about
¾ the way from the bright star to the faint one.
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Now move on to Step 3.
What to do if your finder field of view is too small to see enough stars to navigate by
Some magnifying finders won’t give you a wide enough view to show
enough stars to navigate by, particularly when there is a lot of light
pollution. Your finding device is critical to your enjoyment of your
telescope. Many people simply accept their fate and struggle. It makes
more sense to address the problem by replacing the finding device. For
smaller telescopes a non-magnifying finder is often the most useful. What
I recommend is to either replace your magnifying finder with a nonmagnifying variety, or add a non-magnifying finder to your telescope. If
you have room for both, there is no reason not to have two finders.
Step 3: Look Through Your Telescope
Now look through your telescope. Remember, it should have the widest-field
(lowest power) eyepiece already in it. It helps if you have previously focused
on a bright star too. After having a look, refer to the Eyepiece View of the
chart. Remember, what you see in the eyepiece will be what is drawn within
the circle on the chart. There may be some rotation depending on the
position of your head. How big is the target object supposed to appear? Is
there an obvious pattern of stars nearby? Now go back to the telescope and
look again. Do you see it?
It’s Ok if you don’t see your target. Note any star patterns in the eyepiece
and memorize them so you can recognize this spot when you see it again.
Now very slowly and very carefully move the telescope just a bit while you
are looking through it. Don’t be surprised if it moves in the opposite
direction you expect it to. Try moving a bit in another direction, but don’t
lose your starting point. Once you have a feel for how the telescope moves,
try moving away from your starting point and then back again. Don’t go too
far at first, moving only to the edge of your original field. Do this in different
directions, keeping an eye out for your target object. If you still haven’t
found it, try moving farther away in each direction, always coming back to
where you started. You should come across your target very close nearby. If
you still can’t find it start over. It may be that you made a mistake and
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pointed in the wrong part of the sky. That’s ok too. Finding objects manually
with your telescope is a skill. It will take some practice to get good at it.
Summary
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Adjust your finding device so that it points exactly where the telescope
is looking well ahead of time.
Always start with your lowest-power widest-field eyepiece.
Focus on a bright star before hand.
Begin with the Naked Eye View of the chart to find the general area of
the sky.
Use the Finder View of the chart to refine the pointing of the telescope.
Refer to the Eyepiece View of the chart to get an idea of what to look
for, particularly how big the object should appear.
Search the area with your telescope if the object isn’t already in the
telescope field of view.
You should get pretty good at finding things after some practice. If not, try
to identify where you are having trouble so you can make improvements. It
may help to adjust the finder chart on the screen again by zooming views in
or out or changing their relative sizes.
If you use a magnifying finder you may find that you are having trouble
pointing the telescope initially. If this is happening you may want to consider
adding a simple red-dot finder alongside your magnifying finder. Use the
red-dot finder to get you pointed initially, then move to the magnifying
finder.
Observing Deep Sky Objects in the Telescope
Always start with your lowest-power eyepiece in your telescope. Your
eyepieces will usually be labeled in mm. Start with the eyepiece with the
largest number, E.g. 22 mm.
Use the previously discussed method for finding the target in the sky then
look through the telescope. Focus so that any stars you see are tiny and
sharp. If the object is large and obvious you should see it immediately or by
nudging the telescope a bit you will find it nearby.
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If the object is small and faint you may need to refer to the Eyepiece View of
the SkyTools Finder Chart for your telescope. Be sure to also select the
lowest-power eyepiece at the top of the window when using the chart so it
will match what you see in the sky. Look for obvious patterns in the brighter
stars on the chart, both inside and surrounding the eyepiece view circle.
Then try to identify similar patterns in the brighter stars you see in the
telescope. Keep in mind that sometimes the view in the eyepiece will be
rotated a bit from what is shown on the chart, depending on the angle of
your head when you look into the telescope. Once you have gotten your
bearings it should be apparent where the target object will be.
If you don’t see your target immediately, try looking just to the side of
where it should be rather than directly at it. This is called averted vision, and
helps you see faint objects because your eyes are less sensitive to light
when you look at something directly.
Once you find your object, try averted vision even if it was obvious. You may
be surprised how much additional detail this can bring out. Take your time!
Many people take a quick glance and then they are done. It pays to be
patient because atmospheric conditions can change quickly, revealing
momentary detail. It also pays to learn how to really look. Try describing
what you see to yourself or for your log book. How many different things can
you notice about the object? Making a simple sketch can also help you see
details that you didn’t notice at first.
If the object appears small consider trying higher magnification. There are
two ways to increase the magnification: you can select a highermagnification eyepiece (with a smaller number in mm) or you can use a
Barlow lens with the same eyepiece. A typical Barlow lens doubles the
magnification of any eyepiece. The eyepiece is inserted into the Barlow and
then the Barlow + eyepiece is inserted into the telescope.
Insert a Barlow or the eyepiece that gives you the next highest
magnification. You may have to re-focus. You will notice that the stars will
be a bit fuzzier and it will be more difficult to bring them to sharp focus. The
field of view will also be smaller such that small movements of the telescope
may put things out of the field of view. If your telescope doesn’t
automatically track the sky, the objects in the telescope will drift out of view
more quickly. For these reasons, it becomes more difficult to use your
telescope as you go to higher magnifications. In general, only use higher
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magnifications for small objects in order to better see them. If you want to
show something to a friend or family member it is a good idea to use the
lowest magnification possible.
Finally, take some time to think about what you are looking at. Look with
your mind as well as your eye. It can be fun to research your targets before
you go outside. For instance, if it’s a galaxy, how far away is it? How big is
it? How long would it take to cross this galaxy at the speed of light? Imagine
how many stars there must be in this little fuzzball, and how many more
planets. Could someone be looking back at the Milky Way right now? Right
now…? Or would that be millions of years ago? What then, does “right now”
really mean?
Keeping an Observing Log
It is a good idea to keep a record of your observations. Many observers keep
a simple log book where they record the date and time, location, telescope,
and their impressions or experiences. For some, the logbook becomes a
record that can be referred to—if not treasured—years later. The sky throws
many interesting and unexpected things our way. My own logs have
recorded many interesting things over the years, including a meteor storm,
observing Mars when it was close in 2003, close-approaching asteroids, the
spots left from the impact of a comet on Jupiter, and the Great Comets HaleBopp and Hyakutake.
One simple way to log your observations is to make hand-written notes on
your printed SkyTools Finder Charts (if you use them). In time you may
want to use software for recording your notes. The other editions of
SkyTools have a sophisticated logging tool that automates the recording of
associated information, such as your telescope and eyepiece, and has an
extensive search capability.
Seek Out Your Local Astronomy Club
Most communities have a local astronomy club full of amateur astronomers
who love to share what they have learned about observing. Attending an
event or meeting of a nearby club can be a great way to get tips on using
your telescope and to make friends who are also interested in astronomy.
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Things to Look At in the Sky
The Bread and Butter of Backyard Astronomy
This chapter will introduce you to the objects that every sky observer cuts
their teeth on. They are bright, easy to find, and interesting to look at.
Most of these objects are found in the Starter Objects observing list. Start by
selecting the Starter Objects observing list in the planner. At the top, select
the night you want to observe along with your location and telescope or
binoculars. Select Objects at or near their best and Easy. This will filter out
those objects that aren’t good to look at tonight. With your mouse drag the
red vertical line on the right side of the NightBar graphic until it reads the
time you want to go to bed (or otherwise finish observing).
Note that if the moon is bright some of the fainter objects won’t appear, but
they will return later in the month. Check the box next to Sort in best
observing order.
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The remaining objects in the list are the ones to look at on this night. Note
the time under the Begin, Best and End columns. You should have a look at
each of these objects within this period of time in order to get a good view.
Using the Nightly Observing List Generator
SkyTools can also make a list of these and similar showpiece objects custom
made for any date, location, and telescope or binoculars. Start by selecting
the night on which you want to observe in the planner along with your
location and telescope or binoculars. If you will be going to bed at a certain
time drag the red vertical slider on the right side of the NightBar to your
bedtime.
Next open the Nightly Observing List Generator from the button on the
button bar at the top of the window. Select Showpieces – a list of objects to
impress. Click the Create Observing List button.
The dialog will close and the new observing list will appear in the planner.
Remember, this list is for a particular night, location and telescope. Select
Reset Filters from the blue Observing List menu. We won’t need filters for
this list because the objects were preselected to be good on this night.
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Check the box next to Sort in best observing order to sort the list in the
order to observe each object.
Print the list and take it outside or print finder charts for each object and
take those out with you.
Some of the objects in the list aren’t in this chapter. There may be some of
the brighter and easier deep sky objects too. These may be a little harder to
find at first than those listed in this chapter, but they make great objects for
when you are ready to move beyond the easy targets described here.
The Moon
The moon is the natural place to start in the sky. It is bright, easy to locate,
and endlessly fascinating in any telescope.
You usually want to observe the moon when it is high in the sky in order to
get the clearest view. Open the SkyTools planner and set your date and
location. Select the Sun, Moon and Planets observing list. Select Reset Filters
from the blue Observing list menu.
Find the moon in the list and click on it to select it. Look for the red-dashed
line on the NightBar graphic at the top of the planner. This line tells us how
high the moon is in the sky over the course of 24 hours, from noon on one
day until noon the next. About what time is the red-dashed line highest on
the graphic? That will generally be the best time to view the moon. Note the
times listed under the Begin, Best, and End time columns. Begin is the time
you should start looking at the moon, Best is when you will have the best
view, and End will be the latest you should be looking. If this observing
window in time isn’t when you can go out and have a look, then it is best to
wait for another night. Otherwise, take your telescope out and point it at the
moon during the time indicated. You probably won’t need a finder chart for
the moon. Finally, don’t ignore the moon during daylight; it may appear a
little washed-out but it is still fascinating to look at.
Pass your cursor over the NightBar and keep it still for a few seconds. A flyup will appear that gives information about the night, including the phase of
the moon.
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One of the great things about the moon is that our view changes daily. The
phase of the moon tells us what the view will be tonight. The moon also sets
an hour later each night, so the time to see it will change every day as well.
The phases of the moon go from New, to Waxing Crescent, to First Quarter,
to Waxing Gibbous, to Full, to Waning Gibbous, to Third Quarter, to Waning
Crescent, and then back to New again in about a month. Each phase lasts a
few days, but the moon will still change noticeably from day to day. The
main phases are:
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New – when the moon is between us and the Sun. At this time the
moon isn’t observable. Because the moon isn’t lighting up the night
sky these nights are usually the darkest, and therefore the best nights
to look at fainter objects.
First Quarter – when the moon appears in the evening sky after
sunset. In short order it will follow the sun down to the western
horizon.
Full – when the moon rises in the east at the same time the sun sets
in the west. The entire moon is lit up on these nights and it will be up
all night. But this is in fact a poor night to look at the moon because
there aren’t any shadows highlighting the features; it will seem
washed out.
Third Quarter – when the moon appears in the sky after midnight,
rising to its highest at sunrise. Most people miss seeing the moon near
this phase because they are asleep. Consider that an observing
challenge.
New again.
The changing phase is the key to observing the moon. Each night the line
between light and dark will move , eventually sweeping over the entire
visible surface twice during the month. This line between light and dark is
called the terminator. If you were standing on the moon near the terminator
the sun would be very low in the sky and everything would have long
shadows. It is these long shadows that provide definition for the lunar
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features, giving them a sharp appearance and bringing out detail that can’t
be seen on other nights. In this way each night between New and Full will
highlight a different slice of the moon. As the shadow works across the moon
again between Full and New, the same slices will be highlighted as before,
but lit from the other side, again providing a different view. Most people only
look at the moon in the evening when it is between New and Full. If you ever
get tired of the view try staying up later to watch it when it is between Full
and New instead.
If using a telescope, always start with your lowest power eyepiece. This is
the eyepiece with the largest number written on it. Only insert an eyepiece
with a smaller number in it after you have centered the moon. If you have
more than two eyepieces, move to each smaller number in order. The
eyepieces with the smallest numbers (e.g. 5 mm) will be the most difficult to
use. The view will be the most jittery and the most blurry. What you want to
do is find the eyepiece that gives you the sharpest and most comfortable
view. The best way to know which eyepiece is the best is to try them all.
SkyTools can label the major features of the moon for you. Right-click on the
moon in the observing list and select your telescope from the menu. A finder
chart will appear. You may want to temporarily turn off the finder and naked
eye views by toggling the view buttons at the top of the chart. Try selecting
different eyepieces at the top to look for the best view of the moon. You can
also zoom in or out via the zoom buttons on the button bar. If you don’t see
any labels, open the View Controls and check the box next to Moon/Planet
Features on the Labels tab.
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The Sun
The sun can be fascinating to view with your telescope, but you must always
be very careful. Looking at the sun through the telescope can permanently
blind you! So unless you have a special solar filter never do this. The best
solar filters are the ones that fit over the end of the telescope. Your
magnifying finder can also cause permanent eye damage, so always leave
the lens caps on it. If you don’t have a lens cap, place a thick piece of cloth
over the front end of the finder and use a rubber band to hold it in place. If
there are others around when you have the telescope outside during the
daytime always make sure to explain the dangers of looking at the sun to
them.
You can buy telescopes designed specifically
for looking at the sun, such as the Coronado
PST. These telescopes have filters built in that
not only protect your eyes but make the view
more detailed and interesting by isolating
certain colors of light. These telescopes will not
only show sunspots but surface detail and
prominences along the edge of the sun.
Previewing the Current Sun Image
SkyTools can show you an image of the current sun downloaded over the web
so you will know ahead of time whether there are any interesting sunspots or
other features. This image is from the SOHO solar monitoring satellight.
Select the Sun, Moon, and Planets observing list in the planner. Select the
date, location, and your telescope or binoculars. Select Reset Filters from the
blue observing list menu. Find the sun in the list and double-click on it to open
the Object Information window. Click the Update Sun Image from Web button
to download the latest image. Targeting the sun in a chart will also
automatically update the image. Click on the Action Menu and select View
Scope/Binocs and then choose View “your telescope or binoculars” to open the
finder chart. The sun will be the target object. You may want to temporarily
close the finder and naked eye views via the toggle buttons at the top of the
chart. The eyepiece view will show the sun as it currently appears. Note that
the sun will not be drawn in full detail if the background of the chart has been
changed to a solid light color (such as white).
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If you don’t have a solar telescope or solar filter you can still view the sun by
projection. The light of the sun is projected onto a light surface such as a
piece of paper. Even binoculars can be used to project an image of the sun.
How you best go about this depends on your telescope; if you can fix a piece
of paper to a clipboard and then attach the clipboard to something so much
the better. But you can also simply project the image on a wall or floor or
hold the paper in your hand. As always, start with your lowest power
eyepiece (the one with the largest number in mm). To target the sun simply
look at the shadow of your telescope or binoculars. You want to point the
instrument such that its shadow is as small as possible. This will be when it
is pointing directly at the sun.
You will see light on your projection surface when properly pointed. This is
the disk of the sun. Adjusting the distance from the telescope to your
projection surface will change the size of the projected solar disk. Try to
make it as large as you can without making it too faint to see detail. Adjust
the focus until the edge of the sun is sharp. Typically you should be able to
make out a few sunspots. An interesting project is to trace the sunspots and
return the next day to see how they have moved or changed.
The Stars
I received my first telescope when I was ten. I took it outside and pointed it
at a bright star and worked the focusing knob. What I discovered was that I
could make the star larger and smaller by adjusting the focus; if I wanted to
I could make it swell up to a big interesting ball with lots of sparkling
appendages. Like many people I was confused because I didn’t know what a
star was supposed to look like.
The thing to remember about stars is that they are all very, very far away.
They are in fact so far away that no telescope can magnify them more than
you can see with your naked eye. Your telescope or binoculars will make
stars appear brighter and reveal more faint stars but they cannot make the
stars appear larger; they will always remain tiny points of light. The best
focus then is when the star is as small and sharp as you can make it.
But even though a star can never show detail, that doesn’t mean there isn’t
any reason to look at them. Everywhere stars congregate, whether in a
cluster, a chance grouping, close double star pair, or a dense starfield in the
Milky Way, the view is always pleasing; and when seen together the subtle
colors of the stars become much more apparent. Even singly, a very bright
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and colorful star such as Antares can sparkle like a diamond in the telescope
and following the changes in brightness of variable stars can be fun and
interesting.
Double Stars
Stars sometimes come in pairs or triplets. In some cases the two stars are a
chance alignment in the sky but in others they are connected by gravity,
orbiting around one another. We can even follow their movement if the stars
are close enough to us. These are called Long Period Binary stars. It takes
many years to see the stars move, and many decades for them to orbit
around once.
Regardless of how they come about, close double stars are always
interesting to look at in the telescope. Some great star pairs for small
telescopes are: Alberio, Antares, Epsilon Lyr (the famous Double-double in
Lyra), Mizar, and 70 Oph.
You don’t need a dark sky to observe double stars, so they are great to look
at from an urban location or when moonlight interferes with the fainter stuff.
How good your views will be will depend on how high the stars are in the sky
and how steady the air is. Some nights the stars will swell and jump around
because of the unstable air. It may be that you can’t split the pair at all
under these conditions; they may just look like a single blurry blob. On
another night, or later that same one, the air may be steadier. That is when
you will get a good view and the stars will be split into a pair. On some rare
nights the sky will be so steady that you will have a very memorable view,
and for some close pairs it may take such an exceptional night to split them
at all. This is why we must always come back to some targets again and
again, searching for that perfect view on a perfect night.
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Planning to Observe Double Stars
Start by selecting a double-star observing list in the planner, such as the
Double Stars for Small Telescopes or Some Colorful Double Stars. Select
the date you plan to observe, your observing location, and the telescope
you plan to use. Make the following selections on the planner:




Objects at their best only
Detectable
Drag the red vertical line on the right side of the NightBar until it
indicates the time you want to go to bed (optional)
Check the box next to Sort in best observing order
The objects that remain will be your best targets on this night. Double
stars are at their best when high in the sky; it is important to observe
each during the observing window indicated by the Start, Best, and End
time columns. The stars will already be ordered in the best order to view
them.
You can also use the Nightly Observing List Generator to automatically
create a list of double stars custom made for your selected date, location,
and telescope. To do this, first enter the date, location, and telescope into
the planner. Set the time you want to go to bed via the right slider on the
NightBar (optional). Open the Nightly Observing List Generator from the
button bar. Select Double stars – appealing double stars.
Variable Stars
Plotting the changes in brightness of variable stars can make for a great
project. There are many reasons for a star to vary in brightness; entire
textbooks have been written about them. Many stars pulsate in size,
changing their brightness, and sometimes stars will eclipse each other. Two
good variable stars for small telescopes are Mira and RZ Cas.
Mira is a pulsating variable star in the constellation Cetus that changes in
brightness from 2nd magnitude (a bright naked-eye star) to 10th magnitude
(a faint star requiring binoculars or a small telescope to see). It takes about
330 days to go from faint to bright and then back to faint again (this is
called the period of the variable star). It can be fun to estimate how bright
Mira is every clear night by comparing it to surrounding stars. Keep track of
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how bright it is for many months and then plot the magnitudes on a graph.
Astronomers call such a graph a light curve.
Planning to Observe Variable Stars
Mira and RZ Cas are included in the Starter Objects observing list. Also
select the date you plan to observe, your observing location, and
telescope you plan to use. Choose Objects at or near their best and
Detectable. Optionally drag the red vertical line on the right side of the
NightBar until it indicates the time you want to go to bed. If Mira or RZ
Cas are good to view this night they will be listed.
Stellar Eclipse Predictions
SkyTools can tell you when the next eclipse of RZ Cas will occur. Select
the Starter Objects observing list in the planner. Set you date, location
and telescope or binoculars at the top of the planner. Select Reset Filters
from the blue Observing list menu. Find RZ Cas in the list and double-click
on it to open the Object Information window. The times of upcoming
eclipses will be listed under Variability. Look for an upcoming eclipse that
will occur when RZ Cas is above the horizon at night. RZ Cas is above the
horizon all night long from locations in the middle-latitudes (and north) of
the northern hemisphere.
Another good variable star is RZ Cas. “Cas” is the abbreviation for the
constellation Cassiopeia. Most variable stars are given names made up of
letters (RZ) or numbers (e.g. V3456) plus the abbreviation of the
constellation they are in. RZ Cas is really two stars orbiting very close to one
another. They orbit so close that even the biggest telescope can’t split them
apart from so far away; we only see the combined light of both stars.
Every 28 hours or so one star passes in front of the other, blocking the light
of the star behind. When this stellar eclipse happens the apparently single
star we see in the telescope appears fainter. Professional astronomers can
learn a great deal by analyzing the light curve of an eclipsing pair. In fact,
this is the main way they have to measure the sizes and masses of stars. An
eclipse of RZ Cas lasts for about 5 hours, making a great project for a single
night. During the eclipse the star will appear to dim by more than a
magnitude.
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Jupiter
Jupiter has been called the “playground of the amateur astronomer.” The
motions of the four Galilean moons and cloud patterns that rotate in and out
of view always provide something new to see.
The Jupiter observing season is welcomed by sky watchers everywhere and
its presence is sorely missed at other times of year; it pays to know when
Jupiter is well-positioned for observation. SkyTools can, of course, help you
with that.
In binoculars you may be able to make out Jupiter’s moons. They will appear
as tiny points of light on either side of the planet or they may simply make
the planet look elongated in an odd way.
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Planning to Observe Jupiter
Open the SkyTools planner and set your date and location. Select the Sun,
Moon and Planets observing list. Select Reset Filters from the blue
Observing list menu.
Click on Jupiter in the list. Note the Begin, Best and End times for Jupiter.
If they are blank then Jupiter is likely too close to the Sun. In that case
you will need to wait several months for the Jupiter observing season to
begin. Otherwise the Begin, Best and End times will tell you the best time
of night to view it. The red-dashed-line showing the altitude of Jupiter on
the NightBar is also useful. Unless you stay up all night, what you want to
see is Jupiter well above the horizontal green line during the evening.
To the naked eye Jupiter will look like a very bright star. Right click on
Jupiter and select View Naked Eye to see where to look for it. It will
typically be the brightest star in that part of the sky, if not the entire sky.
You should also notice a slight yellowish hue. Lastly, Jupiter will stand out
for another, more subtle, reason. Because Jupiter isn’t a point of light like
a true star it will twinkle less, shining more steadily than the stars.
Where Jupiter really shines is in a telescope. Even the smallest telescope will
show the moons strung out to either side of the planet. You will also be able
to see the disk of the planet itself; look for light and dark bands and notice
that the planet isn’t perfectly round.
Jupiter is so big that you would have to place 22 earths side to side in order
to reach all the way across it. It is also far away, some 5 times farther away
than the earth orbits the sun. What we see in a telescope is the tops of
clouds. In fact, Jupiter is all atmosphere, with no rocky surface to stand on
like the earth’s. If you were to visit Jupiter there would be no way to land,
but we can imagine being on an airship floating in the clouds. If you were to
look back at the earth from Jupiter it would appear as a bright bluish star. In
your telescope the earth would look tiny—probably too small to make out
any detail.
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Observing the Moons of Jupiter
The bright moons of Jupiter in order of distance from the planet are: Io,
Europa, Ganymede and Callisto. The moons orbit in circles around Jupiter,
but from our vantage point we always see them from the side. They appear
to move back and forth about the planet, first moving out to one side, then
back across or behind the planet, and out to the other side. Unless they
happen to be strung out just right all on one side, you can’t tell which one is
which from how far away from the planet they appear to be.
Io is the closest and orbits the most quickly, taking 1 day and 18 hours to go
all the way around once. It looks like a straw-colored star, always near the
planet. Io moves fast enough that if you watch it for over an hour or more
its motion becomes obvious. Europa is next out from the planet and takes
over three days to go around Jupiter. It looks white in the telescope.
Ganymede is next. It is the largest and brightest, with a slight orange-yellow
tint. Ganymede takes more than a week to orbit. Finally, Callisto is the
farthest from the planet and the faintest, taking over 16 days to move to the
opposite side of Jupiter and then slowly come back to where it started. It is
said to have a very slight blue-gray hue.
In time you may be able to tell which moon is which from how they look in
the telescope, but the differences in appearance and color are very subtle.
Identify the moons of Jupiter with a SkyTools Finder Chart
1. Select your date, location and telescope at the top of the planner.
2. Select the Sun, Moon and Planets observing list.
3. Right-click on Jupiter in the list and select View “your telescope” to
open a finder chart.
4. Optional: temporarily close the naked-eye and finder views (but
don’t forget to put them back when done).
5. Click on the eyepiece selection at the top and choose Best Detail.
6. If the moons aren’t labeled, click in the eyepiece view and then
open the View Controls. Select the Labels tab, turn on the Primary
Planets labels, and make sure that All Labels On/Off is checked.
7. Optional: depress the Real Time button on the button bar to show
Jupiter as it looks right now.
8. Optional: set the time step to 30 minutes and click the time-step
forward button to see the motions of the moons.
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Not only are the moons always moving, but they can also pass in front of or
behind the planet, cast a shadow on the cloud tops, and be eclipsed as they
pass into the shadow of Jupiter.
The moons orbit with a slight tilt, which changes
with our seasons. They often pass directly in front
of or behind the planet (a transit), but sometimes
they miss, passing above or below. When in front
of Jupiter they appear as a small bright spot that slowly moves from east to
west. Unfortunately they can be very difficult to spot against the bright
clouds. But the shadow of the moon is more easily visible. These shadow
transits can be dramatic to watch in the telescope, appearing as a small dark
spot on the planet.
Sometimes a moon will pass behind Jupiter, suddenly disappearing on the
eastern limb or reappearing on the western limb. But as with transits these
can be difficult to see clearly. Much more dramatic is an eclipse, where the
moon suddenly passes into or out of the planet’s shadow. The shadow of
Jupiter often extends off to one side. As a result the moon may appear to
drop out of view for no apparent reason. Sometimes the shadow is so far off
to one side that the moon may disappear and then later re-appear on the
same side of the planet.
To find out if any of these satellite events are going to occur open the Object
Information window. You can do this by double-clicking on Jupiter in your
observing list or by double-clicking on Jupiter on your chart. The Synopsis
will list the events that will be visible that night, if there are any.
Venus and Mercury
Mercury and Venus are both inferior planets. Mercury is small, neither has
any moons, and the weather is definitely not as good as it is in our
neighborhood. But that’s not why they are called inferior; this is just a term
for planets that orbit closer to the sun than the earth.
Planets that orbit closer to the sun than we do move quickly and never
appear to get very far away from the sun in our sky. This means that the
only time they are high in the sky is when the sun is too. Although with
proper care and equipment it is possible to observe them in daylight, most
of the time we look for them just after sunset or just before sunrise.
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If you are familiar with the motions of the moons of Jupiter you can think of
Venus and Mercury moving about the sun in the same way that Jupiter’s
moons move around their parent planet; these planets seem to go back and
forth, moving off to one side, then passing in front of or behind the sun
before moving to the other side. When on the western side of the sun we
can see them rise before the sun does in the morning, with the sun following
them up into the sky. When they are on the east side of the sun we can see
them set after the sun sets, following the sun to the horizon.
Although always a slave to its master, the sun, Venus can get far enough
away from it that it is pretty easy to see. It can also become very bright.
You may have heard of Venus described as the evening star or the morning
star. Even non-sky watchers notice Venus sometimes. When it is higher in
the sky and very bright there is always a corresponding increase in UFO
sightings. Binoculars will definitely help you spot Mercury, but they aren’t
going to show any detail.
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The main thing to look for in the telescope will be the phase.
Both planets show phases like the moon does. Galileo turned
his little telescope toward Venus in 1610 and saw that it had
phases. That’s when he knew for certain that the sun is the
center of our solar system rather than the earth, as was
commonly believed.
Mercury and Venus are “full” when behind the sun, and “new” when in front
of it, so these phases aren’t typically observed. When they reach their points
in our sky farthest from the sun they display a quarter phase; we see half
the planet lit and half in darkness. The lit side will always be on the same
side as the sun. That’s for an obvious reason, if you stop and think about it.
Although they pass between us and the sun regularly, it turns out that the
tilt of the orbits keep Venus and Mercury from crossing (or transiting) in
front of the sun most of the time. Instead they pass above or below it. Only
rarely does a transit occur. Viewing a transit is essentially observing the sun,
so see the chapter on observing the sun for details and warnings. The
planets will appear as small black spots against the sun’s disk.
Mercury is fainter and doesn’t stray nearly as far from the sun. This makes it
much more challenging to see. A clear horizon and just the right timing are
critical for spotting it.
To your eye Mercury will appear as a star and you will typically be looking
for it in twilight. Binoculars can really help in spotting it. In the telescope
Mercury will be smaller than Venus and because we must look at it when it is
close to the horizon it will usually look blurry due to all the air we are looking
through.
Spotting Mercury at all is something to be proud of. Seeing it in your
telescope is a big accomplishment
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Catch Venus in the Sky using SkyTools
Select the Sun, Moon and Planets observing list. Select Reset Filters from
the blue Observing List menu. Check the box next to Sort in best
observing order.
Find Venus in the list and click on it to highlight it. Turn your attention to
the NightBar graphic. The red-dashed line is the altitude of Venus over
time. We are looking for the time of the night when the red line is above
the horizon when the sky is dark. Is it in the morning (right side of
graphic) or the evening? It’s possible that Venus is too near the sun to be
seen at either time if you picked an unlucky date. Note the time under the
Best column for Venus. This will be the best time to see it on this night. If
it is a dashed line then you can’t see it this night. If so, try changing the
date by several months. If there is a time listed then this is the time it will
be best observed. The Begin and End times tell you the time period during
which you should try to see it.
Double-click on Venus to open the Object Information window. At the
bottom the observing Synopsis will appear. This will tell you a lot about
the visibility of Venus, now and in the near future. Look for the date when
it will be at greatest western or eastern elongation. Venus will be highest
in the sky around this date, visible after sunset for eastern elongation and
before sunrise at western elongation.
Finally, right click on Venus and select View Naked Eye. The Naked Eye
chart will appear and Venus will be the target object, indicated by cross
hairs. The chart will automatically open at the best time to see Venus.
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Saturn
Saturn may be the most stunningly beautiful object in the sky. Many
astronomers, amateur and professional, can trace their interest in
astronomy back to the first time they saw Saturn in a telescope. When
Saturn is caught high in the sky on a night when the air is steady it can
literally make people gasp the first time they see it. It is not uncommon for
those seeing Saturn for the first time to accuse the telescope owner of
somehow faking the view. I recall one young woman who looked and then
pulled her head back sharply, exclaiming, “That’s not real!” with an odd mix
of accusation and confusion. It may have only just dawned on her at that
moment that planets were real; more than myth and more than astrological
symbol, but a place that you could potentially visit.
Planning to Observe Saturn with SkyTools
To find out whether Saturn is good to look at tonight, open the SkyTools
planner and set your date and location. Select the Sun, Moon and Planets
observing list. Select Reset Filters from the blue Observing list menu.
Click on Saturn in the list. Note the Begin, Best and End times. If they are
blank then Saturn is likely too close to the Sun. You will need to wait
several months until the Saturn observing season begins. Otherwise they
will tell you the best time of night to view it. The red-dashed-line showing
the altitude of Saturn on the NightBar is also useful. Unless you stay up all
night, what you want to see is Saturn well above the horizontal green line
during the evening.
To the naked eye Saturn will look like a very bright star. Right click on
Saturn and select View Naked Eye to see where to look for it. It will
typically be one of the brightest stars in that part of the sky, if not the
entire sky. You should also notice a slight yellowish hue. Like Jupiter,
Saturn will also stand out because it won’t twinkle, shining more steadily
than the stars.
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Like Jupiter, Saturn has an observing season which changes slowly from
year to year as it drifts among the stars.
In binoculars Saturn will look mostly starlike, but you may be able to
glimpse the rings as a bulge in the planet.
In the telescope the rings can be stunning. Look for gaps and for the shadow
of the rings on the planet. Also look for the shadow of the planet on the
rings. But be patient. Your first look may be disappointing and that’s ok.
Some nights are simply better than others. Most of all, don’t just have a
quick look. Looking for just a moment is a commonly made mistake. Get as
comfortable as you can, and sit if possible. Relax. Take your time. Opening
your other eye often helps. Wait for those fleeting moments of steady air
when the details will jump out. Try to catch what you see in those moments
and store it away. If you don’t see much, or if the view is blurry, then try
again later or on a better night when Saturn is high in the sky and the air is
steady. Those amazing views I wrote about don’t occur every night. You
must look again and again in order to catch them!
Observing the Moons of Saturn
The moons of Saturn are fainter than those of Jupiter but any telescope will
show Titan, the brightest. Tethys, Dione, and Rhea are easily visible in a 3inch (75 mm) telescope. Iapetus varies in brightness with the side of Saturn
it is on; it is brightest when west of the planet, and at this time may be
glimpsed in 5-inch (128 mm) or even smaller telescopes. Enceladus might
be glimpsed in a 5-inch telescope as well on nights when it is far from the
planet and the air is steady.
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Identify the Moons of Saturn using a SkyTools Finder Chart
1. Select the date, location and telescope at the top of the planner.
2. Select the Sun, Moon and Planets observing list.
3. Right-click on Saturn and select View “your telescope” to open a
finder chart.
4. Optional: temporarily close the naked-eye and finder views (but
don’t forget to put them back when done).
5. Click on the eyepiece selection at the top and choose Best Detail.
6. If the moons aren’t labeled, click in the eyepiece view and then
open the View Controls. Select the Labels tab, turn on the Planet
Satellight labels, and make sure that All Labels on/off is checked.
7. Optional: depress on the Real Time button on the button bar to
show Saturn as it looks right now.
Note:SkyTools will show you all the moons, not just the ones you can expect to
see. So keep in mind which ones you may not be able to see in your telescope
(such as Mimas and Hyperion).
Mars
There is little point in looking at Mars in your telescope unless it is near an
opposition, which occurs roughly every 26 months. These are the times
when Mars is closest to the earth, which translates to Mars looking larger in
the eyepiece. If you want to see the features of the red planet, the larger it
appears the better. An opposition isn’t just a single day; it marks the time
when Mars is at its closest, but Mars will be a good target for at least a
month before and after the opposition date.
Not all oppositions are the same. The best oppositions occur every 16 years
or so. During the opposition in 2003 Mars appeared the largest in recorded
history, reaching a diameter of 25 arc seconds. But by 2010 it was much
smaller, with a maximum diameter of only 14 arc seconds, nearly half the
size as seen in 2003. In 2012 it will be about the same size as in 2010. It
won't be until 2014 that it starts getting larger again. The next really good
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opposition will be in 2018 when it will be 24 arc seconds in diameter. After
that it will begin to shrink once more.
Upcoming Oppositions
Date of Opposition
2012 March 3
2014 April 8
2016 May 22
2018 July 27
Maximum Size in arc seconds
14”
15”
18”
24”
How high in the sky Mars gets from your location will also change from
opposition to opposition; as always, the higher the better. Timing is
everything when it comes to observing Mars.
When near opposition Mars is unmistakable, appearing to the naked-eye as
one of the brightest, if not the brightest, stars in the sky. The ruddy orangeyellow hue makes it stand out.
Any telescope will show Mars as a small reddish disk. An experienced and
patient observer can see many interesting details in even a 4-inch (100 mm)
telescope. No matter what the size of your scope, patience and persistence
are the keys to success.
The enemy of the Mars observer is the earth's fickle atmosphere. Always
look at Mars when it is highest in the sky.
On nights when the air is steady much detail should be visible. Be sure to
take your scope outside well before you observe and point it at the sky to let
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it cool to the same temperature as the surroundings. Most scopes will take
an hour or more to cool.
Many people believe that you need a dark sky to observe Mars, but this isn't
the case. Mars can be observed from your back yard or garden as long as
there is steady air. Try not to observe Mars over a building or any other
significant source of rising heat.
Planning to Observe Mars
Assuming Mars is near opposition, open the SkyTools Nightly Planner and
select the Sun, Moon, and Planets observing list. Enter your date, and
select your location and telescope. Note the Begin, Best and End times for
mars. This will be the time of night you should try to observe it.
Some nights will simply have steadier air (better seeing) than others, so it is
important to get out and observe on as many nights as possible. Have a look
at a bright star, such as Sirius. Is it dancing and flickering, perhaps even
changing colors? The more steadily it shines the better the seeing. But even
if Mars is nothing but a blur in your scope patience can really pay off. If the
seeing is very poor have a look at something else for a while and come back
later. In any event, be prepared to stare at Mars for at least an hour. Try to
get as comfortable as possible. Sit down if you can. Even on nights of poor
seeing there are often moments of great clarity. These brief moments are
when the details become apparent.
Using red or orange color filters can help bring out dark features. Wratten 25
or 23A filters are often recommended. A blue or violet filter can enhance the
cloud features.
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Previewing Martian Features
SkyTools will show you the detail you can expect to see in your telescope.
Open the SkyTools Nightly Planner and select the Sun, Moon, and Planets
observing list. Enter your date, and select your location and telescope.
Find Mars in the list and right-click on it. Select View “your telescope” from
the popup menu.
Click in the “eyepiece” selection hypertext at the top of the Finder chart
window and select Best Detail. Mars will be drawn in the eyepiece view
with approximately the same detail you will see in your telescope. It does
this by adjusting the size of Mars, as displayed on your screen, to match
the detail of the telescope; Mars may appear small and lack detail, just as
it will in the telescope.
To see the major features labeled, click in the Eyepiece View, open the
View Controls and select the Labels tab. Ensure that the boxes next to All
Labels On/Off and Moon/Planet Features are checked.
The most prominent dark markings to look for are Syrtis Major, Mare
Acidalium, Utopia, Mare Erythraem and Sinus Sabeus. These markings vary
from year to year and may even show changes over a few months.
Look for the polar ice caps too. Depending on the tilt of Mars you may see
one or the other.
Transient features to look for are the clouds that come and go. They appear
as white spots. Dust storms can also appear. They look like yellowish clouds
that start out small, yet may possibly grow to encompass the entire
planet. There is currently no way to predict when or where these dust
storms will appear.
Because the Martian day is only 40 minutes longer than the earth's, you will
be presented with the same side of Mars at the same time on successive
nights. If you observe every night at midnight, for instance, it will take over
40 nights to see the entire planet slowly rotate into view. A passage of five
days will reveal a 1/8th turn of Mars in the eyepiece. On the other hand, you
can also see a 1/8th turn by observing Mars 3 hours later.
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Looking at Mars as often as possible during opposition offers not only a
better chance for one of those moments of magnificent clarity, but the
opportunity to observe changing features. The time-honored technique is to
draw what you see during those brief moments of clarity. A piece of paper
and a pencil with circles pre-drawn on it are all you need.
Mars has two moons, Phobos and Diemos, but they are only visible to
experienced observers with large telescopes.
Naked-Eye Comets
Every few years a bright naked-eye comet appears in the sky. When one of
these comets appears SkyTools can help you observe it, automatically
obtaining the necessary data from our web site.
There are a lot of misconceptions about comets. Cartoons often show them
whizzing by very fast, which isn’t accurate. Many people confuse comets
with meteors. When you see a quick streak of light in the sky what you are
seeing is a meteor, not a comet. A typical comet hangs for weeks or months
in the sky, night after night, moving slowly among the stars.
A comet is a small icy body, usually somewhere between 100 yards (100 m)
and 25 miles (40 km) in diameter. This tiny body, called the nucleus, is
made of rock, dust and various ices.
Comets orbit around the sun like the planets do, except that they don’t
usually orbit in circles. Their orbits are very long, stretching from close to
the sun to far out beyond Pluto. When they are far
from the sun they are impossible to spot in even the
largest professional telescopes because they are so
small. But as they approach the sun, the heat melts
the ice. Out in space the ice skips being a liquid and
goes right to being a gas (like steam). Eventually a
very large cloud of gas surrounds the nucleus; this
cloud, or coma, is bright enough to be visible.
Sometimes the solar wind will blow this gas into a
long tail, but many fainter comets don’t show much of a tail, if at all. The
very bright comets that can easily be seen with the naked eye are the ones
that typically have the long tails.
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Planning to Observe a Bright Comet
To find out if there are any comets currently visible open the SkyTools
planner and select the Current Objects observing list. If your computer is
connected to the Internet the latest version of this list will be downloaded
from our web site. You can also force the download by selecting the
Update “current objects” list from web menu item from the blue Observing
List menu. Select the date, location and your binoculars or telescope.
Choose Reset Filters from the Observing List menu.
Most of the objects in the list will be asteroids. A few may be novas or
supernovas. Any comets will show up with a little comet icon. Click on the
Mag column heading to sort in magnitude (brightness) order. The
brightest object (object with the smallest magnitude) should now be at
the top. If not, click again to reverse the sort order. Any comets near the
top of this list may be good targets.
Highlight a comet (if there is one!) and note the Difficulty. If the difficulty
is obvious or easy this is a good comet to try for. Note the Begin, Best and
End times (the time period during which you should look for the comet).
To make a finder chart right-click on the comet and choose either View
Naked Eye if a very bright naked-eye comet, or View “your telescope or
binoculars.” This will open a chart at the Best time with the comet as the
target object. You could print this chart and take it outside at the time
indicated on the chart to see the comet. See the Finding Targets at the
Telescope topic for instructions to use the finder charts at the telescope.
SkyTools will plot the size of the comet’s coma on the charts, giving you a
good idea of what to look for in the telescope. A line drawn from the
center of the comet circle tells you the direction a tail would appear, if
there is one.
There are two reasons for a comet to become very bright: if it passes close
to the sun, or if it passes close to the earth. If passing near the earth, like
comet Hyakutake in 1996, it may become very large, and perhaps be seen
high in the sky away from the sun, but will only be visible for a short time.
The tail of Hyakutake stretched more than half way across the sky one night,
but was only near its brightest for a few days.
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If passing near the sun, like comet Hale-Bopp did in 1997, it may be bright
for many weeks. But because these comets are brightest near the sun, our
best views of them typically come just after sunset or just before sunrise.
Some comets can become so bright they can be glimpsed in daylight, such
as comet McNaught in 2007.
Often a comet will only be seen at its best from the far northern or southern
hemisphere. If a bright comet comes along that can only be seen from the
southern hemisphere, such as comet Lovejoy in late 2011 and early 2012,
those in the northern hemisphere may have to be satisfied with pictures. Of
course, the reverse is also true.
Finding Out More about a Comet
Double click on the comet in the observing list to open the Object
Information window. The Synopsis will tell you what the visibility of this
comet will be in the next 30 days and when it will be at its brightest
and/or highest in the sky.
Comets also break down into two different types by their orbits. All comets
originally come from far out beyond Pluto and most will make a single dive
toward the sun, passing close and then heading back out into deep space
never to be seen again. There is no way to predict when this will happen.
These comets are often discovered as they are approaching the sun and we
may have anywhere from days to weeks or months to plan for their arrival.
Other comets have their orbit altered by a close pass to a planet—usually
Jupiter. In time these comets end up in a more circular orbit. These comets,
called Periodic Comets, come back again and again, like comet Halley which
returns every 76 years, and we can predict when they will return. Some
comets brighten enough to be seen in small telescopes every 4-5 years, but
these comets seldom become bright enough to be seen to the naked eye.
Even if a comet is bright enough to be seen with the unaided eye, be sure to
have a look at it in your binoculars and your telescope!
Fainter comets that can only be observed in a telescope are much more
common. See the Telescopic Comets topic in the next section for more about
observing these more difficult objects.
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Open Clusters
When stars are born they form together in bunches. After the stellar winds
have driven away the gas and dust from which they were formed, what
remains is a cluster of stars. Our galaxy is full of these open star clusters, so
called to distinguish them from their cousins, the massive globular star
clusters that surround our galaxy. Globular clusters are discussed in Taking
Observing to the Next Level.
No two open clusters are alike. Some are close groupings of hundreds of
stars while others are loose groups of less than a dozen. Each has its own
charm and there are open clusters that are tailor made for binoculars and
telescopes of every size.
Many people feel that star clusters are the most beautiful of the deep sky
objects, with their often colorful stars described as jewels in the sky.
Photographs don’t truly capture their beauty. And unlike galaxies and
nebulas they are not greatly diminished by light pollution.
The most obvious and well-known clusters can be seen with the naked-eye.
These are excellent targets for binoculars and small telescope: the Hyades,
Pleiades, Beehive, and the Double Cluster (h Per and Chi Per).
The Hyades are a prominent part of the northern-hemisphere winter sky.
They look like a large letter “V” and form the nose of Taurus (the bull). The
bright red star Aldebaran lies at the top left of the “V”. With the “V”
standing upright, the smaller Pleiades lie off to the right.
The Pleiades are also known as the Seven Sisters, M45, and the Milk Dipper.
In Japanese they are called Subaru and are featured in the logo for the car
company of the same name. They are sometimes confused with the Little
Dipper because they look like a tiny dipper in the sky. Most people can see
six stars with the unaided eye but many more become apparent in
binoculars and small telescopes. Large telescopes typically have too small of
a field of view to fit them all in. The brightest stars in the Pleiades are:
Alcyone (Eta Tau), Atlas (27 Tau), Electra (17 Tau), Maia (20 Tau), Merope
(23 Tau), Taygeta (19 Tau) and Pleione (16 Tau).
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The Pleiades are young in cosmic terms—a mere 100 million years old. The
Earth is 45 times older than the stars in this cluster. When they were being
born the Dinosaurs walked the Earth. The Pleiades are also among the
closest star clusters, about 380 light years distant. The light that enters your
eyes from these stars left 380 years ago so you are seeing them as they
appeared then. The reverse is also true: an observer looking back at us from
the Pleiades would be seeing the Earth as it appeared in the mid
seventeenth century.
The Beehive Cluster is located in the constellation Cancer and is also known
as Praesepe and M44. This cluster is large and loose, absolutely requiring a
wide field of view to take it all in, making it a fine object for binoculars.
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The Double Cluster lies in Perseus. As the name implies it is actually two
clusters lying near each other. They are known to SkyTools by their
individual names, h Per and Chi Per. These clusters are smaller and fainter
than the others we have mentioned so far. To the naked eye they appear as
a small elongated hazy patch in the Milky Way. Many faint stars often take
on the appearance of a fuzzy or hazy patch until we look more closely with
binoculars or a telescope. Binoculars will begin to reveal individual stars and
a telescope will show these clusters in wonderful detail.
These clusters are remarkably young, only 3 and 6 million years old. They lie
at a distance of about 7000 light years. When the light left these stars it was
5000 BC, human civilization was still in the Stone Age and the Sahara was a
land of flowing rivers and green forests.
Planning to Observe an Open Cluster
Use the SkyTools planner find out which cluster is good to look at tonight.
Start by selecting the Starter Objects observing list. Select the date you
plan to observe, your observing location, and telescope or binoculars you
plan to use. Make the following selections on the planner:




Objects at or near their best
Easy
Drag the red vertical line on the right side of the NightBar until it
indicates the time you want to go to bed (optional)
Check the box next to Sort in best observing order
The objects that remain will be your best targets on this night. Pick a
cluster and right-click on it. Select View “your telescope or binoculars” to
see a finder chart on the screen. See Finding Targets at the Telescope for
instructions for finding your cluster in the sky.
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The Milky Way
You may read accounts from experienced observers describing the beauty of
an edge-on spiral galaxy in their big telescope as seen from a dark sky site.
But the biggest, brightest, most amazing galaxy in the sky is our own! You
don’t even need a telescope to see it and binoculars will reveal more
wonders than can be seen in any other galaxy, even in the largest telescope.
Unfortunately you may not be able to see the Milky Way from your backyard
in the city. This is because the lights from nearby cities wash the sky out,
making it difficult to see. You may have to wait until you go on vacation or a
camping trip to get a good view.
One of the great joys of observing is scanning the Milky Way with binoculars.
The dark areas look like places where there are fewer stars, but in fact you
are looking at huge clouds of gas and dust that are blocking the light from
the more distant stars. Other areas contain vast star clouds, where there are
so many faint stars that they look like a starry cloud.
If you are using a telescope simply point it somewhere in the Milky Way and
slowly move the telescope to see what you can discover. Look for star
clusters and dark nebulas, or find your own special piece of sky with
patterns of colorful stars.
Easy Deep Sky Objects
Everything in the sky that is outside of our solar system and not an
individual star is a Deep Sky Object. Most look best in photographs where
they show detail and color not visible in the telescope. Nonetheless, deep
sky objects can be spectacular in their own right as long as you don’t expect
to see a lot of detail and color.
The best starter deep sky objects, other than the open clusters and double
stars already mentioned, are: The Great Nebula in Orion (M42), The
Andromeda Galaxy (M31), Lagoon Nebula (M8), Ring Nebula (M57), the
Omega Nebula (M17), Omega Centauri, M4, Crab Nebula (M1), Whirlpool
(M51), the Eta Carinae Nebula, and the Large and Small Magellanic clouds.
Some of these objects may not be visible from your latitude.
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Planning to Observe an Easy Deep Sky Object
To see which of these you can look at tonight open SkyTools and select
the Starter Objects Observing List. Enter the date, select your location,
and telescope or binoculars.
Choose Objects at or near their best, and Easy. Check the box next to
Sort in best observing order.
Hover the mouse pointer over the NightBar graphic at the top. If it says
“Never completely dark. Full Moon”, many of these objects will be filtered
out of the list. You may want to try a night several days later when the
moon is no longer full. Similarly, if it says First Quarter moon, you may
want to wait a week or two (after full moon) because it won’t be fully dark
until when the moon sets, which may be very late.
The Great Nebula in Orion
M42 is a large cloud of glowing gas with stars embedded in it. If you can see
the constellation Orion as the hunter figure, then there is a vertical line of
fainter stars in the middle of his lower body that make up his “sword.” Upon
closer inspection in a telescope the middle star will be revealed to be a
bright nebula. So not only is M42 one of the premier nebulas in the sky, but
it is also easy to locate. Once you know where it is, you can always find it
again. For these reasons there is no better deep sky object to start with and
you will return to it again and again.
Of M42 Walter Scott Houston wrote, “No amount of intensive gazing ever
encompasses all its vivid splendor.” As always, start with your widest-field
lowest-magnification eyepiece. If the air is steady, move to successively
higher magnifications. At the heart of the nebula lies the Trapezium, a close
grouping of four stars that becomes more discernible at higher
magnifications.
The nebula is a complex of individual clouds of gas and dust about 20 light
years across and 1600 light years away. Deep within the nebula, unseen to
amateur telescopes, are small pockets where new stars and planets are
forming.
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The Andromeda Galaxy
M31 is the brightest nearby galaxy of our Local Group of galaxies, if you
don’t count the Magellanic Clouds which are satellites of our own galaxy, the
Milky Way.
M31 is bright enough that it can be seen with the naked eye from a dark
location as a long oval smudge of light. Like M42, it is also fairly easy to
locate off to the side of a bright star in the constellation Andromeda.
The M31 galaxy is not all that different from our own. A being located inside
M31 would look back at our Milky Way galaxy and see much the same thing
that we see. In the telescope it looks like an oval haze that is brighter near
the middle. No detail is discernible. All those billions of stars, great clusters,
nebulas like M42, and great dark clouds of dust—rendered a mere haze by
the enormous distance. Yet when you consider that the combined light of a
billion stars in M31 has travelled 2.5 million years across the great void
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between galaxies destined to one day end its journey in your eye, how can
you see it as anything but utterly majestic?
When that light left the Andromeda galaxy, humans did not yet exist.
The Ring Nebula
M57 is a planetary nebula; a cloud of glowing gas that has been expelled
from an aging star. Much smaller than M42 or M31, it is nonetheless bright
and very simple to find. M57 lies between two bright stars in the
parallelogram of Lyra.
As always start out
with your widest-field
lowest-magnification
eyepiece. But
remember M57 is
small, so take care to
inspect all the stars in
the field. Look for one
that isn’t a star-like
point of light. It may
take a little hunting the
first time to spot it; look for a small circle of light. Once you have it spotted
try successively higher magnifications, looking for the eyepiece or eyepiece
+ Barlow that offers the best view.
The distance to M57 isn’t accurately known, but we can say that it is several
thousand light years away. At its center lies an exotic white dwarf star that
is too faint to be seen in small telescopes. The nebula is the outer layers of
this once normal star that were blown into space in the process of dying. The
remaining white dwarf has collapsed down to a size similar to that of the
earth. It is like a hot coal left over from a fire. Yet it is still very hot and very
bright if seen up close—some 500 times as bright as our sun!
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Taking Backyard Observing to the Next Level
In this chapter we will look beyond the bright beginner objects. The objects
detailed here are fainter and more difficult to find with your telescope. Most
are out of reach of binoculars.
SkyTools will help you find these more difficult objects. There are many
observing lists in SkyTools Starter Edition, including the classic Messier list.
You have already met some of the various M-objects from this list. The
Caldwell Objects and our own 310 Objects for Small Telescopes have enough
interesting targets to keep you going for a long time. If you have the Turn
Left at Orion handbook the objects in that book are also in SkyTools as
observing lists. There are also many more double stars to look at in the
Double Stars for Small Telescopes and Colorful Double Stars observing lists.
Planning to Observe Deep Sky Objects
Many of the targets in this chapter are the so-called Deep Sky Objects.
They all require a similar approach when planning to observe them. Start
by selecting an observing list in the planner, such as the Messier Objects.
Select the date you plan to observe, your observing location, and
telescope you plan to use. Make the following selections on the planner:




Objects at or near their best.
Visible (any difficulty).
Drag the red vertical line on the right side of the NightBar until it
indicates the time you want to go to bed (optional).
Check the box next to Sort in best observing order.
The objects that remain will be your best targets on this night. The darker
the sky the better for most of these objects, so if you happen to pick a
night near full moon there may not be many remaining.
It is important to observe each object during the observing window
indicated by the Start, Best, and End time columns. The objects will
already be ordered in the best order to view them. The times to observe
each object tend to bunch together when twilight ends or the moon rises
or sets. Note which targets have long observing windows; these are less
critical to observe at a given time. You can observe these in the middle of
your observing period.
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Uranus and Neptune
These planets aren’t typically bright enough to see with the naked eye so
they will be more challenging to locate than Jupiter or Saturn.
Like all outer planets, Uranus and Neptune have an observing season which
changes slowly from year to year as they drift among the stars.
Planning to Observe Uranus or Neptune
To find out whether one of these planets is good to look at tonight, open
the SkyTools planner and set your date and location. Select the Sun,
Moon and Planets observing list. Select Reset Filters from the blue
Observing list menu.
Click on the planet in the list. Note the Begin, Best and End times. If they
are blank then the planet is likely too close to the sun. If so you will need
to wait a few months for the observing season to being. Otherwise they
will tell you the best time of night to view it. The red-dashed-line showing
the altitude of the planet on the NightBar is also useful. Unless you stay
up all night, what you want to see is the planet well above the horizontal
green line during the evening.
You won't need a dark sky to observe Uranus or Neptune in a telescope
because they are relatively bright. Any telescope will show them as a tiny
point of light, and from a darker site even binoculars will work. A 4-inch
(100 mm) or larger scope will show the tiny blue-green disk of Uranus when
the air is steady. About half the size of Uranus, Neptune is perhaps too small
to see the disk in telescopes smaller than 6 inches (150 mm). Neptune will
look like an oddly-colored blue star.
Uranus was encountered by Voyager 2 in 1986, leaving
us a wealth of information regarding the planet and its
satellites. At a distance from the sun of over 19 AU this
gas giant takes over 84 years to orbit once. The first
planet discovered in modern times, it was found by the
great 18th century observer William Herschel in 1781.
Herschel, a musician by trade, spent his nights
surveying the sky. He wrote, "In examining the small
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stars in the neighborhood of H Geminorum I perceived one that appeared
visibly larger than the rest..." Herschel's discovery was by no means an
accident, as is often stated. He and his brother Alexander built the largest
telescopes of the day--the first practical application of the reflecting
telescope invented by Newton. Assisted by his sister Caroline, Herschel set
out to observe every star in the sky. As he put it, "In a regular manner I
examined every star in the heavens and that night it was its turn to be
discovered." Biographies are full of stories that reflect his great zeal for
observing, including slipping out between the acts of a play.
Unlike the other planets, Uranus is very highly tilted with respect to its orbit;
it lies nearly on its side, tilted by some 98o. It seems unlikely that a planet
would form with such a large tilt. Did Uranus collide with another planetsized body sometime in the distant past?
Uranus is composed of gas above ice above a small rocky core. The cloud
tops we observe in the telescope are composed primarily of methane in a
clear atmosphere of hydrogen.
Neptune was encountered by Voyager 2 in 1989,
leaving us a wealth of information. This giant
planet takes over 160 years to orbit the sun.
Neptune is some 17 times more massive than the
earth and has a diameter of nearly four times that
of our planet. Like Uranus, Neptune is composed of
gas above ice above a small rocky core. The cloud
tops we observe in the telescope are composed
primarily of methane.
The moons of Uranus and Neptune can’t typically be seen in smaller
telescopes. An 8-inch scope is required to observe the brighter moons of
Uranus and Neptune’s largest moon Triton. Note: that SkyTools will show
you all the moons on the chart, not just the ones you can expect to see.
Globular Clusters
These star clusters are much larger groupings of stars than the open clusters
and they are drawn together into a much more concentrated, spherical
shape. Globular clusters typically have hundreds of thousands of stars all
packed into a tight ball. In a large telescope there may be no view more
breathtaking than the myriad stars of a globular filling your field of view,
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except perhaps for Saturn's rings. Some of the best examples are Omega
Centauri, M13, 47 Tuc, M22 and M15.
Stick to the brighter globulars for the most stunning views. The larger the
telescope, the better the view. Larger telescopes will reveal many of the
individual stars. In telescopes smaller than
6-inches (150 mm) a globular typically
looks like a round hazy spot in the sky
because only a few of the individual stars
can be seen.
Globular star clusters are composed of old
stars. Unlike the open clusters, which form
continuously, the globulars formed very
long ago. The globular clusters of our
galaxy are all approximately the same
age; perhaps formed when our galaxy
collided with another early in its history.
They are found outside of the disk of our galaxy, surrounding the galactic
center. That's why most globulars are visible when Sagittarius is in view; the
center of our galaxy is in this direction.
See the instructions for observing Deep Sky Objects at the beginning of this
chapter for the best way to use SkyTools to observe these objects.
Galaxies
Galaxies are other "island universes" filled with stars, clusters and nebulas of
their own. Many people confuse our galaxy with our solar system. Our solar
system is made up of all the objects that surround our star, the sun. But the
sun is just one star among many billions within our galaxy. Just about
everything you see in the sky with your eyes that is outside our solar
system--the stars, clusters, and nebulas--are all in our own Milky Way
galaxy. It is an immense, disk-shaped structure with perhaps a trillion stars
in it.
The distances to the objects we see around us in our own galaxy are
measured in hundreds or thousands of light years. But other galaxies are
much farther away; even the closest galaxies are millions of light years
distant. The only exceptions are the two companion galaxies to our own
Milky Way; the Magellanic Clouds. The clouds appear as large hazy patches
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to the naked eye. They are located in the far-southern sky and can’t be seen
from mid-northern latitudes.
Galaxies, like stars, often cluster together in groups. Our Milky Way is a
member of one such group, which we call the local group. The two brightest
galaxies in the northern sky are members of our local group: M31 (the
Andromeda galaxy), and M33 in Triangulum. As we saw in the Bread and
Butter of Astronomy section, M31 can be glimpsed by the naked eye as an
elongated hazy patch and appears clearly in binoculars. M33 would be an
easy target for small telescopes, except its light is spread over such a large
area that it never appears more than a round, hazy patch of sky. This makes
it difficult for first time observers. Other local group members are also large,
spreading their light out so much as to make them extremely difficult to see
at all. Keep this in mind when you see the magnitude listed for a galaxy; the
large ones may be difficult or impossible to spot even if they are supposedly
bright enough to see in your telescope. Look instead for galaxies that
SkyTools indicates are detectable or better.
The vast majority of galaxies appear as small hazy patches of sky, revealing
little detail to the eye. Where photographs show many faint stars, spiral
arms, and other details, our eyes typically only see a colorless haze. This is
one of those times when we need to look with our minds as well as our eyes.
Our own galaxy is immense, containing more stars and planets than Captain
Kirk ever dreamed of! Neither the immensity of our galaxy nor the enormous
distances between stars are accurately depicted in the popular media. At the
speed of light it would take 100,000 years to cross it.
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Now imagine if you could go so far away that our galaxy would appear as a
tiny smudge of light that required a telescope to see. This is what other
galaxies represent. Consider that they are so far away the light has travelled
for a very long time to get here, taking millions of years to cross the
immense cold empty space between galaxies, passing between the dust and
stars in our own Milky Way, zipping past the planets in our solar system,
encountering an atmosphere for the first time, entering the optics of your
telescope and ending its journey at… your eye.
There are three main types of galaxies: ellipticals, spirals, and irregulars.
Elliptical galaxies are round or egg-shaped, often with a bright, starlike
center. They look pretty much the same from all directions and are
otherwise featureless. Two of the brighter ellipticals are M87 and M84.
Spiral galaxies are disk-shaped like our own Milky Way. They are flat with a
round bulge at the center, much like a classic flying saucer. Their apparent
shape depends on the angle from which we are viewing them. A face-on
spiral galaxy will generally appear round. The center may appear starlike, or
it may be a round or oval bright spot. Photographs will show winding spiral
arms in such galaxies, but in all but a few cases these arms are invisible in
the telescope. Some good examples of face-on spiral galaxies are M51 and
M33.
At the other extreme we have spiral galaxies seen edge-on. Here the galaxy
appears long and thin, with a thickening in the middle. We may see dark
dust lanes running the length of the galaxy. Such galaxies are often the
most interesting in the telescope. Some of the best examples are the
Sombrero, M82 and NGC 253.
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We see most spiral galaxies from a viewing angle between these two
extremes; M31 being the most obvious example.
Irregular galaxies don’t have regular shapes. Many of these galaxies are
distorted because of a collision with another nearby galaxy.
See the instructions for observing Deep Sky Objects at the beginning of this
chapter for the best way to use SkyTools to observe these objects.
Diffuse Nebulas
Diffuse Nebulas are clouds of glowing gas and dust. Our galaxy is filled with
these clouds, which lie mostly along the Milky Way in the sky. Most of this
gas is dark, it can glow when a hot bright star is nearby . There are two
ways for the gas to glow. Both ways require lots of blue and ultraviolet light
entering the nebula. Massive hot stars are an excellent source of such light.
Unfortunately it is these nebulas that often cause the most disappointment
for beginners who are expecting to see the vivid detail and colors found in
long exposure photographs. Your eye simply can't see color and faint detail
as well as a camera can. So in most cases these nebulas appear as faint,
often irregular, hazy patches of sky.
One of the best nebulas in the sky is M42, an HII region (pronounced “H 2”)
in Orion. This nebula was introduced in the Bread and Butter of Astronomy
section. It may seen as a hazy patch even to the naked eye. In all but the
tiniest of telescopes it forms a beautiful twisting swirling mass of clouds,
usually a pale gray or slight green color. There are some people who claim
to see a tinge of pale red as well. Another good example is the Omega
nebula (M17).
Another kind of a nebula is M1, the Crab Nebula. This one is special because
it is what was left after a massive star exploded in 1054 AD. We call this
kind of nebula a Supernova Remnant. When a massive star ends ita life in a
supernova explosion it can outshine an entire galaxy of billions of stars for
many weeks.
The Crab Supernova was recorded by Chinese astronomers in 1054 and may
have been painted on a rock wall in the American southwest. Today it looks
like an elliptical glow in a telescope, like a small faint cloud in the sky.
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M78 is an example of a reflection nebula. It can be seen in a telescope as an
irregular patch of hazy sky, much like the Crab Nebula. It lies in Orion in the
same general part of the sky as M42. Reflection nebulas glow because the
light from a star is scattered as it passes through a gas cloud in much the
same way that sunlight is scattered by our atmosphere (which makes the
sky blue). It is the dust particles in the cloud that do the scattering. As with
the sky, the blue light is scattered most easily; the other colors tend to pass
right on through but some of the blue light is scattered away in all
directions. If you are off to the side of a cloud it will appear to glow blue
from the light being scattered in your direction. These reflection nebulas are
distinctly blue in photographs, but appear only as a hazy gray in a telescope
because your eye can’t see color in near darkness.
Remember M42 in Orion? The emission nebula (or HII region)? The other
way for a cloud to glow is when the light from the star is absorbed by the
gas atoms and then re-emitted. Hydrogen gas atoms like to absorb
ultraviolet light. When they do their only electron uses that energy to break
free of the atom and go flying off. Eventually it meets another hydrogen
nucleus and recombines to make a hydrogen atom again. When this happens
it must shed the energy it stole before; emitting it in some random direction
as mostly red light. The process at work is similar to that of a neon sign.
Rather than a wide range of colors, the light from these clouds is emitted
over a set of specific narrow colors only. Your eye has trouble with this,
which is why neon signs look so weird. HII regions appear distinctly red in
photographs, but for the most part they too appear as a pale gray in the
telescope.
In fact there is no way to tell one kind of nebula from another in the
telescope, but it is interesting to know how each kind comes about.
See the instructions for observing Deep Sky Objects at the beginning of this
chapter for the best way to use SkyTools to observe these objects.
Planetary Nebulas
Planetary nebulas have nothing at all to do with planets. They were named
long ago before people knew what they were. These nebulas reminded
people of planets because they are small and bright. But in fact they are
another sort of glowing gas cloud.
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Planetary nebulas are formed when a star reaches old age.
These stars will swell to many times their original size, to
the point where they puff their outermost layers of gas out
into space. The hot star at the center makes this gas glow
much like an HII region, except in this case we mostly see
glowing gas other than hydrogen, such as oxygen.
In the telescope most planetary nebulas appear slightly blue or green,
depending on the observer. To some people, like me, all but the most
colorful planetaries merely look pale gray.
These nebulas come in all sizes and shapes. The famous Ring Nebula in Lyra
is a classic example for beginners because it is bright, looks great, is not too
small, and is easy to find between two naked-eye stars.
The best planetaries are small enough that they are well defined and bright.
Be aware that some planetaries are listed as being very bright but they are
so large that the light is spread over a wide area. This makes seeing them
very difficult. At best some of these appear as a sort of brightening of the
background sky. A good example is the Helix. To avoid the really hard ones,
pick planetaries that SkyTools says are detectable or better.
Just finding one of the hard ones in a small telescope is an achievement.
Many deep sky observers will tell you that the hunt is what they enjoy the
most. The more difficult it is to find an object in a particular telescope the
more satisfying it is when you finally convince yourself that you have found
it. If you are looking for a challenge then pick a planetary that SkyTools
indicates is difficult or challenging, but be sure that it is at or near its best
(green stoplight indicator).
Some other classic planetaries for any telescope are the Dumbbell, the
Saturn Nebula, Ghost of Jupiter, and the Owl.
See the instructions for observing Deep Sky Objects at the beginning of this
chapter for the best way to use SkyTools to observe these objects.
Dark Nebulas
These are clouds of gas and dust that hide the stars behind them. The gas in
interstellar space is accompanied by very tiny grains of dust, much like that
found in cigarette smoke. If the cloud is dense enough, these grains scatter
and absorb enough light as to render the stars beyond invisible. These
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nebulas are perhaps best enjoyed with a pair of binoculars or a telescope
with a wide field of view.
The summer Milky Way is a particularly good place to look for dark nebulas.
From a dark site you will see large dark lanes even to the naked eye. Sweep
along Sagittarius and Scorpius, and all the way north to Cygnus, in a
telescope or binoculars. Look for patches where the stars seem to be
missing.
Some of the better examples of dark nebulas are the Coal Sack and
Barnard's E.
The most famous dark nebula is the Horsehead. This nebula in Orion is
famous from photographs, but is very, very difficult to see visually in a
telescope—even big ones. The distinctive, horse-head shape is outlined by
the dark nebula against a very faint diffuse nebula. The problem is that if
you can't see the diffuse nebula, then you won't be able to make out the
shadow of the horsehead. Seeing this one is not for beginners!
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See the instructions for observing Deep Sky Objects at the beginning of this
chapter for the best way to use SkyTools to observe these objects.
Asteroids
An asteroid (or minor planet) is a small rocky or metallic body in our own
solar system that orbits closer to the sun than Jupiter. Most of the asteroids
reside in the so-called asteroid belt between Mars and Jupiter. The largest
and brightest asteroid is Ceres, which is also classed as a dwarf planet like
Pluto. Ceres can become as bright as magnitude 6.7; not quite bright
enough for most people to see it with the naked eye. It is possible to spot in
binoculars and easy in small telescopes. Ceres is about 300 miles (490 km)
in diameter.
Some of the other brighter asteroids are Vesta, Pallas and Juno. The asteroid
belt has been estimated to contain as many as a million asteroids larger
than 1 km. As of this writing there are over 280,000 known, but the number
is always growing. Most of these are too faint to be seen in small telescopes.
Asteroids are like planets in that each one has an observing season, or time
of year when they are at their best and brightest. Most are best observed
near opposition. Opposition is when the asteroid is in the opposite direction
of the sun, which means it will be high in the sky in the middle of the night.
Most asteroids are also at their closest, and thus brightest, when they are
near opposition.
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In the telescope asteroids look like stars. The only way to tell them apart is
to wait for several hours to see if it moves.
Planning to Observe an Asteroid
Asteroids that are near opposition each month and observable in small
telescopes are included in the Current Objects observing list. Open this list
in the SkyTools planner. If your computer is connected to the Internet the
latest version of this list will be downloaded from our web site
automatically.
Select the date, location and telescope. Don’t use a date too far from the
current date or the information for the asteroid won’t be accurate. Set the
difficulty to detectable unless you are feeling up to more challenging
asteroids. Unlike deep sky objects, asteroids are moving targets that
change in brightness. This makes the observation quality reported by
SkyTools much less useful. So set the observation quality to All and ignore
the status in the observation quality column.
Any visible asteroids will show up in your observing list with an asteroid
icon. Click on an asteroid to highlight it.
Note the Begin, Best and End times (the time period during which you
should look for the asteroid).
To make a finder chart, right click on the asteroid and choose View “your
telescope” in the menu. This will open a chart at the Best time with the
asteroid as the target object. You can print this chart and take it outside
at the time indicated to see the asteroid. See the Finding Targets at the
Telescope topic for instructions to use the finder charts at the telescope.
SkyTools will plot the asteroid as a star on the charts. Make sure the
target cross hairs are enabled in the View Controls for the eyepiece view
so the asteroid will be indicated.
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Pluto
Whether you call it a Planet, Dwarf Planet, or large Trans-Neptunian Object,
the Pluto in the sky is still the same as it ever was in a telescope: it still
looks like a faint 13.8-magnitude star that moves a little from night to night.
Pluto can be observed reliably in a 6-inch (150 mm) telescope. Experienced
observers with darker skies can spot it in smaller telescopes. If SkyTools
says it is visible in your telescope then Pluto represents a fine challenge!
Once you have some experience finding things in the sky give this one a try.
Choose a night when SkyTools says it is at its best (green light icon) and be
sure to look near the time SkyTools says is best. You will need to be good at
matching star patterns because, after all, it looks just like any other star.
But unlike stars there is one way to make sure you actually saw it: come
back a few nights later and see if it has moved. Make a sketch of the stars
you see in your eyepiece on your first attempt to compare to later. The star
you identified as Pluto should have moved.
As usual with astronomy there’s not much to see, yet it is special. Pluto is
the most distant object within the solar system that you can see in your
telescope. It lies at least 32 times farther away from the sun than the earth,
so far away that its light takes over 4 hours to reach your telescope. No
spacecraft has visited Pluto so we can't say for certain what it looks like up
close, at least until the New Horizons spacecraft flies by in the summer of
2015. Pluto is so far away that even though New Horizons is the fastest
spacecraft ever flown, the journey will take 9 years.
Pluto is a mere 2200 km in diameter (about
60% that of the moon) and its largest
satellite, Charon, is about half that size.
The discovery of Charon in 1978 was
important because the orbit tells us the
mass of Pluto directly. This plus the
diameter of Pluto tells us its density, which
in turn gives us a clue as to what Pluto is
made up of. In fact the density of Pluto is
very similar to Neptune’s moon Triton,
which is made of a mixture of rocky materials and water ice.
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One thing about Pluto is quite clear: it is very cold! Looking back at the sun
from Pluto the sun would appear as nothing more than a bright star. From
Pluto the earth would be nearly invisible as a faint speck of light lost in the
sun's glare.
Planning to Observe Pluto
Pluto is included in the Sun, Moon, and Planets observing list. Open this
list in the SkyTools planner.
Select the date, location and telescope. Set the difficulty to visible (any
difficulty). Set the observation quality to Objects at or near their best.
If this is a good time to try for Pluto you will see it listed. Click on Pluto to
highlight it. Note the expected difficulty. If your sky is too bright and/or
your telescope is too small Pluto may be listed as not visible. You may
need to wait for another night when Pluto is higher in the sky or when
there is no moonlight. Otherwise the expected difficulty will be indicated.
Finding Pluto will not be easy if it is listed as difficult or challenging!
Note the Begin, Best and End times (the time period during which you
should look for Pluto).
To make a finder chart, right click on Pluto and choose View “your
telescope.” in the menu. This will open a chart at the Best time with Pluto
as the target object. You can print this chart and take it outside at the
time indicated to find Pluto. See the Finding Targets at the Telescope topic
for instructions to use the finder charts at the telescope.
SkyTools will normally plot Pluto with a little Pluto planet-symbol icon on
the charts, but it can also be plotted as an ordinary star. Use the When
zoomed-out draw planets as… setting on the Misc. tab of the Chart
Preferences to set it the way you want it to be. It may also help to enable
the target cross hairs in the View Controls for the eyepiece view so Pluto
will be indicated.
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Telescopic Comets
The comets you read about on the web or in magazines are the bright ones
that can be seen with the naked eye. These occur infrequently. Many months
or even years can go by between good naked eye comets. But what most
people don’t realize is that on any given night there is often at least one
comet visible in a small telescope. These comets don’t have long tails and
some are harder to spot than others. In the telescope they look like round
hazy balls, similar to a round galaxy. But unlike a galaxy they move from
night to night. That means they can take you off the beaten path to star
fields that few people visit.
You would think it would be simple, but knowing which comets are visible in
your telescope is actually very complicated. The comet information generally
available is insufficient. Even if the magnitude of a comet is accurate, and it
may not be, the magnitude alone is a very poor predictor of a comet’s
visibility. It can be frustrating to look at a spot in the sky and see nothing.
For this reason even many experienced amateur astronomers never even
try. But this is where SkyTools comes in. SkyTools excels at predicting which
comets are visible in your telescope.
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Planning to Observe a Telescope Comet
To find out if there are any comets currently visible to you open the
SkyTools planner and select the Current Objects observing list. If your
computer is connected to the Internet the latest version of this list will be
automatically downloaded from our web site.
Select the date, location and telescope. Don’t use a date too far from the
current date or the information for the comet won’t be accurate. Set the
difficulty to detectable unless you are feeling up to more challenging
comets. Unlike deep sky objects comets are moving targets that change in
size and brightness. This makes the observation quality reported by
SkyTools less useful. So set the observation quality to All and ignore the
status in the observation quality column.
Any visible comets will show up in your observing list with a little comet
icon. If you don’t see any comets listed then there aren’t any currently
visible to you. If you do see a comet, click on it to highlight it.
Note the Begin, Best and End times (the time period during which you
should look for the comet). To make a finder chart, right click on the
comet and choose your telescope in the menu. This will open a chart at
the Best time with the comet as the target object. You could print this
chart and take it outside at the time indicated to see the comet. See the
Finding Targets at the Telescope topic for instructions to use the finder
charts at the telescope. SkyTools will plot the size of the comet on the
charts, giving you a good idea of what to look for in the telescope. A line
drawn from the center of the comet circle tells you the direction a tail
would appear, if there is one. Sometimes telescopic comets do show small
stubby tails.
Double-click on the comet to open the Object Information window. The
Synopsis will tell you what the visibility of this comet will be in the next 30
days and when it will be at its brightest and/or highest in the sky.
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Novas
A nova is a star that brightens suddenly; at least that’s what we see from
the earth. Typically the star we see before the nova is in fact a binary star
system. Orbiting nearby is a white dwarf star invisible to us in the telescope.
A white dwarf star is a star that has collapsed at the end of its life. It is like
a small very hot cinder left over from the nuclear fires that once made it
shine. The two stars orbit very close together--so close that material from
the regular star is siphoned off onto the white dwarf. This star material
collects on the surface of the white dwarf until a sudden explosion of nuclear
fusion occurs. The star briefly comes back to life, burning hydrogen to make
heat and light as it once did long ago. The light of the two stars is hopelessly
blended together in the eyepiece because they are so far away, so we see
this blending of the two stars as a single star that suddenly becomes
brighter. This is the nova. But once the material is burned away the white
dwarf will become lifeless again and the star will appear as it did before.
The bright novas we typically observe may last for many days or weeks.
Afterward the process begins again, but it may take anywhere from a
decade to many thousands of years for the nova to recur.
Some novas are bright enough to see in binoculars, or even to the naked
eye, but most will require a telescope. In the telescope the nova will look
like an ordinary star.
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Planning to Observe a Nova
To find out if there are any novas currently visible, open the SkyTools
planner and select the Current Objects observing list. If your computer is
connected to the Internet the latest version of this list will be
automatically downloaded from our web site.
Select the date, location and telescope or binoculars. Don’t use a date too
far from the current date or the information for the nova won’t be
accurate. Set the difficulty to detectable unless you are feeling up to more
challenging novas. Unlike deep sky objects, novas won’t be around all
year. This makes the observation quality reported by SkyTools less useful.
Set the observation quality to All and ignore the status in the observation
quality column.
The currently visible novas will show up in your observing list with a star
icon. Novas are often labeled as “Nova” followed by the year. But after a
while they will be assigned a variable star designation and henceforth this
is how they will be known. Variable star designations look like XX Cep or
V9999 Oph. If you don’t see any novas listed then there aren’t any
currently visible to you. If you do see a nova, click on it to highlight it.
Note the Begin, Best and End times (the time period during which you
should look for the nova). To make a finder chart right-click on the nova
and choose your telescope or binoculars in the menu. This will open a
chart at the Best time with the nova as the target object. You could print
this chart and take it outside at the time indicated. See the Finding
Targets at the Telescope topic for instructions to use the finder charts at
the telescope.
SkyTools will plot the nova as an ordinary star. Make sure the target cross
hairs are enabled in the View Controls for the eyepiece view so the nova
will be indicated.
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Supernovas
A supernova is the death of a very massive star; a previously faint star
brightens suddenly and unexpectedly. For many weeks or months the
supernova can outshine the combined light of all the billions of stars in its
galaxy.
The last time a supernova occurred within our own neighborhood (in our
Milky Way galaxy) was over 400 years ago. Kepler's supernova was brighter
than any star and almost as bright as Venus. Other supernovas were so
bright that they could easily be seen in daylight. These supernovas should
happen once every 50 years, so we are long overdue. But you don’t have to
sit and wait. Supernovas happen all the time in other galaxies and even
though these are much farther away some are bright enough to be seen in
small telescopes.
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In the telescope these extragalactic supernovas will look like any other star.
You will often be able to see the host galaxy as well. What that point of light
in your telescope represents is beyond imagination. This is a star suddenly
collapsing and then rebounding outward in an enormous explosion, releasing
as much energy as the sun will emit over its entire lifetime. Much of the
star’s material is driven into the surrounding space at enormous speed,
typically 70 million miles per hour (30,000 km/s or 10% the speed of light).
At that speed an astronaut could travel from the earth to the moon in 13
seconds! The shockwave from this explosion expands into the surrounding
interstellar space, collapsing any nearby clouds of gas and dust and at the
same time seeding the clouds with the heavy elements necessary for life. In
time the collapsing clouds may form a cluster of stars and solar systems with
planets.
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Planning to Observe a Supernova
To find out if there are any supernovas currently visible open the SkyTools
planner and select the Current Objects observing list. If your computer is
connected to the Internet the latest version of this list will be
automatically downloaded from our web site.
Select the date, location and telescope. Don’t use a date too far from the
current date or the information for the supernova won’t be accurate. Set
the difficulty to detectable unless you are feeling up to more challenging
supernovas. Unlike deep sky objects supernovas won’t be around all year.
This makes the observation quality reported by SkyTools less useful. Set
the observation quality to All and ignore the status in the observation
quality column.
Any visible supernovas will show up in your observing list with a star icon.
Supernova designations usually start with “SN” followed by the year and
one or more letters. If you don’t see any supernovas listed then there
aren’t any currently visible to you. If you do see a supernova, click on it to
highlight it.
To make a finder chart, right click on the supernova and choose View
“your telescope” in the menu. This will open a chart at the Best time with
the supernova as the target object. You could print this chart and take it
outside at the time indicated to find the supernova. See the Finding
Targets at the Telescope topic for instructions to use the finder charts at
the telescope.
SkyTools will plot the supernova as an ordinary star. Make sure the target
cross hairs are enabled in the View Controls for the eyepiece view so the
supernova will be indicated. Deep Sky Objects should also be turned on; if
the host galaxy is visible in your telescope it will be drawn in the eyepiece
view as well.
Double-click on the host galaxy to open the Object Information window. If
the distance to the galaxy is known, it will be displayed as Light Travel
Time. This is how long it took the light to travel to your eye from the
galaxy in years. So this is also how long ago the supernova actually
occurred. Note that Gyr stands for Giga-years or billions of years.
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Quasars
These are faint starlike objects that are very, very far away. When they were
first discovered in the 1960s they left astronomers scratching their heads.
They would have to be extremely bright to be seen over such vast distances.
What could be that bright yet so small?
In time astronomers worked out what they are. They are the extremely
bright centers of apparently otherwise normal galaxies. Most galaxies have a
supermassive black hole lurking in the center. When one galaxy collides with
another, gas and dust fall toward the center where some of it finds its way
into orbit about the black hole. The immense gravity causes the material in
orbit to emit enormous amounts of energy. This is the quasar at the center
of a galaxy. It can outshine the rest of the galaxy by so much that we can
see it, even though we can’t actually see the galaxy in our telescope. Even
though they are very bright they are also very far away, making them
appear faint.
The brightest quasar is 3C 273 in Virgo. It can be reliably spotted from a
dark site in a 6-inch (150 mm) telescope. It will pose a challenge for smaller
telescopes. Assuming SkyTools says it is visible in your telescope, 3C 273
represents a fine challenge! Once you have some experience finding things
in the sky give this one a try. Choose a night when SkyTools says it is at its
best (green light icon) and be sure to look near the time SkyTools says is
best. You will need to be very good at matching star patterns because, after
all, a quasar looks just like any other star.
You may have wondered why there aren’t more quasars nearby. Given time,
the material will no longer fall into the black hole and the quasar will no
longer shine brightly. Most people believe that black holes "suck", but this is
a myth. Matter is no more likely to fall into a black hole than the earth is to
fall into the sun, and for much the same reason. The motion of the earth
causes it to orbit around the sun rather than fall into it. But given the infall
of enough material, particularly gas and dust, some will eventually wind up
close enough to eventually spiral in. This process is inefficient so it takes
extreme conditions for it to happen. Apparently in the early universe
galaxies collided more often, causing large amounts of gas and dust to fall
toward the galactic center; thus quasars were more common. Today most of
the quasars are "off". When we look out into the universe we are looking
back in time because it takes light time to travel great distances. The farther
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away we look the farther back in time we are looking. Most quasars occurred
long ago, so they are found at great distances.
All this makes quasars much more interesting to ponder than to look at. You
need to look with your mind as well as your eye. When you find one of these
they look just like an ordinary star. It is knowing what you are looking at
that makes them so amazing and worth hunting down. 3C 273 is 2 billion
light years away! That light travelled for 2 billion years–half the age of the
earth—travelling all that time and all that way just to stop in your eye!
See the instructions for observing Deep Sky Objects at the beginning of this
chapter for the best way to use SkyTools to observe these objects.
The Great Red Spot of Jupiter
The famous Great Red Spot (often abbreviated GRS) is an oval seen against
a cloud band of Jupiter. It is very difficult to see in a small telescope because
has faded in recent decades. It can be a challenge to see even for
experienced observers with larger scopes. Your best chance to see this
elusive spot is when Jupiter is high in the sky, the air is steady, and the GRS
is crossing the center line of the planet (within an hour before and after).
Double-click on Jupiter in your observing list to open the Object Information
window. The Synopsis will tell you if the Red Spot is visible on any given
night. Use the eyepiece view of your telescope finder chart to see where to
look for it; set the eyepiece to Best Detail as we did for the moons. For
smaller scopes it may not even be visible on the chart… if not, then you
likely won’t be able to see it in your telescope either.
The GRS isn't an easy target. You need a night of steady seeing and much
patience. It first appears as a large, oval, lighter area of the southern belt.
Keep looking and wait for a moment of good seeing. It is normal for the spot
to appear and disappear. Be patient! Eventually you may be able to make
out a slight "pinkish" or tan hue to the oval.
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Astronomy Nuts and Bolts
How Far is it? – Distances
You might think that knowing how far away something is would be a simple
matter, but in fact it is often difficult to measure distances outside of our
own solar system. Astronomers must be very clever to measure distances
and we have only a rough estimate for many objects. SkyTools will generally
tell you the distance to an object in the Object Information window if it is
known.
For the distance to nearby objects, such as the moon, we use earthbound
measures such as km or miles. But even in our own solar system the
numbers quickly become so large that they have no meaning. New units of
distance have been created in order to make distances more manageable.
The Astronomical Unit (AU) is used in the solar system. One AU is the
average distance between the earth and the sun. An object 3 AU away would
be three times the distance from the earth to the sun. It can be a fun project
to get a feel for these distances by creating your own scale model of the
Universe. The instructions for making such a model are found elsewhere.
When we measure distances to stars, even distances in AU become far too
large. In our own galaxy and to nearby galaxies we use the light year. Light
travels so fast that it appears to move instantaneously. But over large
enough distances it takes time for light to go from point A to point B. For
example, it takes about 8 minutes for light to travel to us from the sun (1
AU). One light year is how far light can travel if you let it go for an entire
year. Remember that even though it has “year” in it, a light year is a
distance, not a time. The nearest star is about 4.3 light years away. Our
galaxy of stars is about 100,000 light years across. The nearest separate
galaxy, the Andromeda Galaxy, is 2.5 million light years away.
Because it takes light many years to get here, in a way we are seeing these
objects as they appeared long ago. The Universe appears to be about 13.7
billion years old, so if we look far enough away we can look back in time to
the beginning of the Universe. That distance would be around 14 billion light
years, or 14 Giga-light years (14 Gyr).
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How Big is it? – Sizing Things in the Sky
The farther away something is, the smaller it appears. If we know how far
away something is in the sky and how large it appears to be, we can figure
out how big it is using simple geometry.
To the sky observer what matters most is how big something appears to be
in the sky. This tells us how big it will appear in the telescope. When we
measure how large something appears to be we aren’t measuring actual
size, but an angle. If you think of the horizon as a circle, a full sweep all the
way around is an angle of 360o. A half-sweep is 180o and a quarter sweep is
90o. It is also 90o from the horizon to overhead at the zenith.
Most objects in the sky are less than 1o in diameter. So to avoid numbers
like 0.001o for very small objects, we split each degree into 60 parts in the
same way that we split an hour into 60 minutes. We call each part a minute
of arc. The “arc” part is to remind us that these aren’t minutes of time. So
1/60th of a degree is 1’ (one minute of arc). Similarly we split each minute of
arc into 60 seconds of arc. So 1/60th of a minute of arc is 1" (one second of
arc). We often use the shorthand of arc seconds and arc minutes when
talking about minutes and seconds of arc. When you see the ’ symbol read it
as arc minutes. When you see the " symbol read it as arc seconds.
The moon is about ½o in diameter, or about 30’. Jupiter is about ¾’ in
diameter, or 45". Very, very tiny things in the sky are less than 1” in
diameter. You won’t be able to distinguish these from stars.
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How Bright is it? – Magnitudes
The brightness of an object in astronomy is measured in magnitudes. The
ancient Greek astronomers grouped the stars into six magnitude classes,
from 1 to 6. The brightest stars were in the first group (1st magnitude) and
the faintest stars were in 6th magnitude group. This brightness scale
represents how bright stars appear to our eyes rather than the actual
intensity of the light. Nevertheless astronomers have adopted a standardized
version of this scale scientifically.
Objects brighter than 1st magnitude can be zero or a negative number.
Venus is often magnitude -4, the full moon is magnitude -12 and the sun is
-27.
The 6th magnitude stars were the faintest the Greeks could see, so the
faintest naked eye stars are around 6th magnitude. You can see 10th
magnitude stars in binoculars and 13th magnitude stars in small telescopes.
An 18-inch telescope under a dark sky can reveal 17th magnitude stars.
Large professional telescopes equipped with sensitive imaging systems can
record stars fainter than 28th magnitude.
For extended (or large) objects such as galaxies or nebulas the brightness is
described as an integrated magnitude. An integrated magnitude is the
magnitude of an equivalent star if you collapsed all the light from the object
into a single point in the sky. The integrated magnitude for a nebula can be
quite misleading; an 11th magnitude star may be easily visible in your
telescope, but an 11th magnitude nebula may not be, depending on the size.
For decades beginning astronomers have struggled with which objects are
visible in their telescopes and which are not, based on these misleading
magnitudes. Fortunately SkyTools takes these other factors into account
when calculating whether or not you can see an object in your telescope so
you need not worry about comparing integrated magnitudes.
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Where is it? – Celestial Coordinates
The most common coordinate system used by astronomers to permanently
locate things in the sky is the Equatorial system. This system is very similar
to the latitudes and longitudes used to measure places on the earth. But
rather than looking down on an earth globe, imagine looking from the inside
out. You would be surrounded by the surface of the hollow globe and it
would look like the sky if you painted stars on it. We call this the celestial
sphere. The earth’s equator and poles are extended out into space and
drawn on this sphere.
Instead of lines of latitude, we have lines of Declination. The Declination of a
star is measure from the celestial equator, to the North and South celestial
poles. A star with a Declination of zero is on the celestial equator. At the
north celestial pole the Declination is +90o; at the south celestial pole it is 90o. Right Ascension is measured around the sphere in the same way that
longitude is measured on the earth, only it is measured in hours rather than
degrees. Just as 360 degrees is all the way around the earth, 24 hours is all
the way around the sky. The use of hours is more convenient for astronomy.
The position of a star might be given as Right Ascension (or R.A.) 12 hours
and Declination (or Dec.) +15o.
Each hour of R.A. is broken into 60 minutes, just like time. Each degree of
Dec. is similarly broken into 60 minutes of arc. So to specify a position we
need two numbers for R.A. and two numbers for the Dec. Here is an
example:
R.A. 12h43.17m
Dec. +15o23.62’
Read this as 12 hours, 43.17 minutes of R.A. and plus 15 degrees, 23.62
minutes of Dec.
You may see a reference to J2000 with equatorial coordinates. The axis of
the earth wobbles over time; after a few years the equator and poles drift
enough that the coordinates are no longer correct. To avoid this problem we
pick a standard equinox—a point in time where we can always agree where
the earth’s poles and equator were pointing. The most common standard
equinox used today is the year 2000. The “J” is added for technical reasons.
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Another common coordinate system is Horizon Coordinates, which measures
the position of an object in the sky relative to the local horizon. This system
isn’t useful for permanently marking a position in the sky because the
coordinates are always changing as the earth turns. But they can be handy
for pointing out the relative altitude and direction of an object at a moment
in time.
A position in the sky is marked by the Altitude above the horizon and the
Azimuth (or compass direction). The azimuth of north is 0o, east is 90o,
south is 180o, and west is 270o. Altitude is measured from 0o at the horizon
to 90o at the zenith (directly overhead).
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What is it Called? – Astronomical Catalogs
Astronomy has a very long and colorful history. Nowhere is that more
apparent than in the myriad names of the stars and other astronomical
objects. Only the most obvious things in the sky have simple ancient names,
such as the sun, moon, planets, and a few of the brightest stars. For
everything else we have designations from catalogs. Here’s how that
generally works: an astronomer compiles a list of objects for some reason.
Perhaps these are objects that are similar, or more often, objects that have
had some property measured. The list is published as a catalog and each
object in the catalog is given a unique identifier. Typically the last name of
the author is combined with some sort of number as a designation. An
example would be Herschel 10; the tenth entry in a catalog by Herschel. In
other cases the catalog itself is given a name and this is used instead of the
last name of the author, particularly when objects are compiled from other
catalogs to make a comprehensive catalog. An example would be the New
General Catalog (known by the acronym NGC). There are also some
designations built around the coordinates of the objects, something which is
more common today.
The result of all this is that any given astronomical object may have dozens
of designations. For example, the bright star Vega is the brightest star in the
constellation Lyra, so it is Alpha Lyrae. It is the 3rd bright star as measured
from the western boundary so it is also called 3 Lyrae. It appeared in the
Henry Draper catalog of spectral classifications so it is HD 172167. It was
observed by the HIPPARCOS satellight and cataloged as HIP 91262. The
Washington Double Star (WDS) catalog lists it as H 5 39A, and on and on.
You will see two special designations used for bright stars. The Bayer
designations label the bright stars in each constellation by lower-case Greek
letter. These are more or less in order from brightest to faintest. The threeletter constellation abbreviation is typically added to the Greek letter. The
brightest star in Orion is Ori (or Alpha Ori). The next brightest is Beta Ori
and so on.
Flamsteed designations also mark the brightest stars by constellation so
many stars will have both Bayer and Flamsteed designations. Stars are
numbered in Right Ascension order (more or less) from the west, with the
constellation abbreviation appended. So the first star in the western side of
Orion is 1 Ori. The next is 2 Ori and so on.
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Some designations are pretty obscure. You may hear an astrophotographer
talk about a Sharpless object, or a deep sky hunter who uses a big
Dobsonian may refer to Abell 16, or even PN G153.7+22.8.
To make things even more interesting there aren’t any hard and fast rules
about how the various designations are written. One source may use “HGC
16” and another may use Hickson 16 in referring to the same object from
the same catalog. If you have an object from a book, magazine, or web site
that SkyTools doesn’t recognize, be sure to click the Designation Help button
to see how SkyTools expects various designations to be formatted. This may
resolve your problem.
All this history means that frustration is inevitable when a web site or
magazine or handbook refers to an object in one way and another source
uses an alternative. Fortunately for backyard observers with small
telescopes most observable deep sky objects are found in the NGC or IC
catalogs. NGC, IC, and Messier numbers are enough to identify most of
these objects.
There are some rare cases where the same object is known by conflicting
NGC or IC numbers via different sources. In particular beware of appended
letters, such as NGC 1206A. Some sources may use a different letter, such
as 1206B, and others may ignore the letter altogether. If you run into this
sort of thing keep in mind that there often isn’t any right or wrong
designation, but rather an interesting story about the history of the object.
Most numerical designations, such as HD 12345, are straight forward. But
double star designations can be trouble. One particularly confounding
convention in the age of computers is the habit of using a Greek letter to
denote some of the more well-known double star observers. The most
prominent of these is the use of the Greek letter  (Sigma) to mean a double
star cataloged by Friedrich Georg Wilhelm von Struve. The Washington
Double Star catalog uses a three letter code for him: STF. Complicating
matters is that there have been other double-star observers named Struve.
You will see Friedrich’s double stars described as  10, Struve 10, or STF 10.
You can use either Struve or STF to look up an object in SkyTools, but is
problematic for most keyboards
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Build Your Own Scale Model of the
Solar System
“Space is big. You just won't believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it's a long way down
the road to the chemist's, but that's just peanuts to space.” –
Douglas Adams
It isn’t possible to grasp the size of the Universe because it doesn’t fit on the
human scale. But we can grasp how much bigger one thing is in relation to
another; if one really big number with a lot of zeros is three times as big as
another big number, then three is something we can relate to.
Textbooks and films are usually pretty terrible at giving us a feeling for how
distances and sizes relate to one another even in our own tiny solar system.
Often the planets are arrayed in front of the sun so that you can see their
relative sizes, but in doing so the relative distances go right out the window.
If there is one thing to understand about the planets, it is that when drawn
to scale, they are never close enough together to fit on the same page of a
book. The same book will often have a second diagram showing the relative
orbits of the planets around the sun. The planets are drawn smaller, but it
isn’t possible to draw them small enough.
One way to see the real scale of the solar system is to go outside and look
up at a planet. But all you will see will be a point of light and usually no
other planets will be nearby. While that is a good lesson in itself, it doesn’t
help you understand how the distances and sizes of the planets relate to one
another.
The best way to do this is to make your own scale model of the solar system
and then walk around in it. We’ve done the calculations for you below based
on the idea that the diameter of the earth is about the width of a human
hair. Draw a dot or circle of the approximate size of each body on separate
pieces of paper. Label each one. You can draw the moon on the same paper
as the earth; measure the distance between the earth and moon in the
table.
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Start by putting the sun someplace, maybe taped to a wall in a long hallway
or on the ground. Place each planet at the distance in the table, measured
from the sun. English and metric measures have been provided. Once you
are finished you should have some feeling for how the distances between the
planets relate to their sizes. Space really is big, isn’t it? Don’t forget that in
reality the planets aren’t all in one direction from the sun. Most people just
line them up. But consider that in reality some are way off in another
direction, making the distances all that much greater.
If the earth were the width of a human hair:
Sun
Mercury
Venus
Earth
Moon
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto (Kuiper Belt)
Alpha Cen
Galactic Center
Diameter
(inches)
Diameter
(mm)
14/32
Pencil dot
Hair width
Hair width
Pencil dot
Large dot
3/64
2/64
1/64
1/64
Pencil dot
17/32
11
0.04
0.09
0.1
0.03
0.05
1.1
0.9
0.4
0.4
0.02
13.5
Orbit Radius
(feet)
Orbit Radius
(meters)
1’ 6”
2’ 9”
3 ‘ 10”
1/8”
5’ 10”
19’ 10”
36’ 6”
73’ 2”
114’ 10”
149’ 10”
200 miles
1.2 million
miles
0.45
0.84
1.2
0.3 cm
1.8
6.1
11.1
22.4
35.0
45.7
330 km
1.9 million
km
You may have some trouble placing Alpha Cen and the Galactic Center at the
correct distance. Alpha Cen is the nearest star to us. Remember, our Milky
Way Galaxy is filled with stars like our sun and Alpha Cen. There are
hundreds of billions of such stars. Alpha Cen is a mere 4.3 light years distant
in a galaxy that is 100,000 light years across. Keep that in mind.
Have a look at a map and find a place that is about 200 miles (330 km)
away from you. Now take a magnifying glass and look at the dot you made
for the earth up close. Imagine a tiny organism on that dot that is so small
you would need an electron microscope to have any chance at all of
detecting it. That’s you.
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Now look at how far away the moon is. That is a very long way for such a
tiny creature to go. While that’s a long way, it is as far as we have gone; no
human being has ever travelled farther than the moon. Imagine that tiny
creature travelling to your other planets. Now that’s really a long way isn’t
it?
Finally, think about that tiny creature traveling those 200 miles to the
nearest star. We’re pretty much back to mind boggling now aren’t we?
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The Greek Alphabet
Bright stars are given Bayer designations, which use lower-case Greek
letters. English keyboards don’t have Greek keys on them so you will often
see them spelled out. They will also need to be spelled out when entering a
designation into SkyTools. As an example, the bright star Vega is called
“Alpha Lyr.” In order to save space on charts the Greek letter is used. So
Alpha Lyr will appear as  Lyr on charts.
Here are the Greek letter correspondences:
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The Constellations
There are 88 constellations. Each has a possessive (or genitive) form which
is used with various star designations. For instance the possessive form of
Cygnus is Cygni. When talking about the constellation we say Cygnus. When
talking about a star in the constellation, such as the star Beta, we use the
possessive: Beta Cygni.
Fortunately there are standard three-letter abbreviations. These
abbreviations are a short-hand notation and are commonly used in various
star designations. The abbreviation for Cygnus is Cyg. Thus the star Beta
Cygni can also be called Beta Cyg. Astronomers often pronounce these
abbreviations such that Beta Cyg becomes “bay-ta sig”.
Constellation
Abbr.
Genitive Form
Andromeda
And
Andromedae
Antlia
Ant
Antliae
Apus
Aps
Apodis
Aquarius
Aqr
Aquarii
Aquila
Aql
Aquilae
Ara
Ara
Arae
Aries
Ari
Arietis
Auriga
Aur
Aurigae
Boötes
Boo
Boötis
Caelum
Cae
Caeli
Camelopardalis
Cam
Camelopardalis
Cancer
Cnc
Cancri
Canes Venatici
CVn
Canum Venaticorum
Canis Major
CMa
Canis Majoris
Canis Minor
CMi
Canis Minoris
Capricornus
Cap
Capricorni
Carina
Car
Carinae
Cassiopeia
Cas
Cassiopeae
Centaurus
Cen
Centauri
Cepheus
Cep
Cephei
Cetus
Cet
Ceti
Chamaeleon
Cha
Chamaeleontis
Circinus
Cir
Circini
Columba
Col
Columbae
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Coma Berenices
Com
Comae Berenices
Corona Australis
CrA
Coronae Australis
Corona Borealis
CrB
Coronae Borealis
Corvus
Crv
Corvi
Crater
Crt
Crateris
Crux
Cru
Crucis
Cygnus
Cyg
Cygni
Delphinus
Del
Delphini
Dorado
Dor
Doradus
Draco
Dra
Draconis
Equuleus
Equ
Equulei
Eridanus
Eri
Eridani
Fornax
For
Fornacis
Gemini
Gem
Geminorum
Grus
Gru
Gruis
Hercules
Her
Herculis
Horologium
Hor
Horologii
Hydra
Hya
Hydrae
Hydrus
Hyi
Hydri
Indus
Ind
Indi
Lacerta
Lac
Lacertae
Leo
Leo
Leonis
Leo Minor
LMi
Leonis Minoris
Lepus
Lep
Leporis
Libra
Lib
Librae
Lupus
Lup
Lupi
Lynx
Lyn
Lyncis
Lyra
Lyr
Lyrae
Mensa
Men
Mensae
Microscopium
Mic
Microscopii
Monoceros
Mon
Monocerotis
Musca
Mus
Muscae
Norma
Nor
Normae
Octans
Oct
Octantis
Ophiuchus
Oph
Ophiuchi
Orion
Ori
Orionis
Pavo
Pav
Pavonis
Pegasus
Peg
Pegasi
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Perseus
Per
Persei
Phoenix
Phe
Phoenicis
Pictor
Pic
Pictoris
Pisces
Psc
Piscium
Piscis Austrinus
PsA
Piscis Austrini
Puppis
Pup
Puppis
Pyxis
Pyx
Pyxidis
Reticulum
Ret
Reticuli
Sagitta
Sge
Sagittae
Sagittarius
Sgr
Sagittarii
Scorpius
Sco
Scorpii
Sculptor
Scl
Sculptoris
Scutum
Sct
Scuti
Serpens Caput
Ser
Serpentis
Serpens Cauda
Ser
Serpentis
Sextans
Sex
Sextantis
Taurus
Tau
Tauri
Telescopium
Tel
Telescopii
Triangulum
Tri
Trianguli
Triangulum Australe
TrA
Trianguli Australis
Tucana
Tuc
Tucanae
Ursa Major
UMa
Ursae Majoris
Ursa Minor
UMi
Ursae Minoris
Vela
Vel
Velorum
Virgo
Vir
Virginis
Volans
Vol
Volantis
Vulpecula
Vul
Vulpeculae
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Selected Observing Resources
Handbooks
Atlas of the Moon, by Antonin Rukl
Binocular Highlights: 99 Celestial Sights for Binocular Users, by Gary Seronik
Deep-Sky Wonders, by Walter Scott Houston
Guidebook to the Constellations, by Phil Simpson
Observers Handbook, by the RASC (Royal Astronomical Society of Canada)
Turn Left at Orion: Hundreds of Night Sky Objects to See in a Home Telescope - and How to
Find Them, by Guy Consolmagno and Dan M. Davis
Web Sites
Astronomy Magazine
http://astronomy.com
Binocular mount plans
http://www.astro-tom.com/projects/binomount/binocular_mount.htm
Comet Chasing
http://comets.skyhound.com
Sky & Telescope Magazine
http://skyandtelescope.com
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Glossary
Angular Diameter - the apparent diameter of an object in the sky in terms of the angle
subtended by the actual size of the object. The diameter of the sun is 1392000 km, but the
angular size in the sky is about 32' (32 arc minutes, or 32/60th of a degree).
Asteroid - a type of minor planet that mostly orbit between the orbits of Mars and Jupiter.
These objects look like stars in a telescope but move slowly across the sky like planets. E.g.
Vesta or Ceres.
Astronomical Unit (AU) - a unit of distance where the mean distance from the sun to the
earth is 1. An object that lies 10 AU from the earth is 10 times as far from the sun as the
earth is.
Averted Vision – the practice of not looking directly at an object in the telescope, but a bit
to one side, in order to make faint things become visible.
Barlow Lens - a device that increases the magnification of any eyepiece, usually by a
factor of two. The Barlow lens is inserted into the telescope as if it were an eyepiece, then
an eyepiece is in turn inserted into the Barlow.
Best Viewing Time – the best time to view an astronomical object on a given night, taking
into account the telescope being used, the type of object, how bright it is, how high it is in
the sky, and how dark the sky is.
Comet - a small icy body that, when close enough to the Sun, displays a coma (expelled
gas and dust that surrounds the object) and sometimes a tail. Comets do not move quickly
across the sky. In most cases they are stationary, moving slowly from night to night like a
planet. What we see is actually the larger coma rather than the tiny icy body itself. Many
comets approach the sun once and then disappear into deep space where they originally
came from. Some are periodic, which means they orbit the sun regularly and come back
again and again. Comet Halley is the most famous.
Dark Nebula - a cloud of gas and dust that lies between the stars. Dark nebulas can only
be seen against a backdrop of fainter stars; the cloud blocks the light of the more distant
stars, leaving the appearance of a dark spot in the sky where few stars can be seen. E.g.
the Coal Sack or the Pipe Nebula
Declination – measured north and south from the celestial equator to the celestial poles
much like latitude on the earth. Often abbreviated Dec., it is measured in degrees, minutes,
and seconds of arc. The Dec. is zero at the equator, +90 degrees at the north celestial pole,
and -90 degrees at the south celestial pole.
Deep Sky Object - clusters of stars, nebulas, or galaxies. These often make interesting
targets in a telescope because, unlike single stars, they are more than points of light. These
are all objects beyond our solar system that are not single stars.
Diffuse Nebula - a glowing cloud of gas in the sky. These are often emission nebulas (or
HII regions) like M42. They can also be reflection nebulas like M78. Although they typically
look colorless in a telescope, HII regions appear red in photographs while reflection nebulas
appear blue.
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Dwarf Planet - an object that orbits the sun that is massive enough to be round but has
not cleared its orbit of other small bodies. Pluto is the archetype dwarf planet. The Asteroid
Ceres is another example. Most dwarf planets orbit in the Kuiper belt, similar to the asteroid
belt but much farther away from the sun. There are now hundreds of dwarf planet
candidates, but few have been officially designated as of this writing.
Ecliptic - the path in the sky that the sun and planets follow. This is also the plane of the
earth's orbit around the sun.
Field of View (FOV) - the angular diameter of the area of the sky you see in a telescope
or binoculars. The field of view is drawn on the SkyTools charts as a circle.
Galaxy - a very large collection of stars and dust and gas. Our own galaxy is called the
Milky Way and includes all the stars we can see in the sky. We can see the disk of our spiral
galaxy as a band of light in the sky. Even though galaxies are enormous, other galaxies are
so far away that they look like faint fuzzy clouds in a telescope. In a dark sky the
Andromeda Galaxy is visible to the naked eye.
Galaxy Cluster - also called Galaxy Groups. A galaxy cluster is one or more galaxies
grouped close together, often seen in the same field. A well-known example of a galaxy
cluster is Stephan's Quintet. Galaxy clusters typically require telescopes larger than 6inches and a dark sky.
Globular Cluster - a large dense cluster of stars that appears like a ball of stars in the
telescope. These clusters typically contain hundreds of thousands of stars and are found in a
halo surrounding the disk and central bulge of our Milky Way galaxy. E.g. Omega Cen or
Messier 13.
Gyr - a Giga-year; one billion years.
Kuiper Belt - a region of our solar system beyond the orbit of Neptune populated by
smaller icy bodies such as Pluto.
Light Year – a measure of distance; the distance that light travels in one year.
Magnification - the apparent increase in size of an object. Binoculars magnify what you
see in the distance. Telescopes do too, but how much they magnify depends on the
eyepiece you are using.
Magnitude - a measure of how bright a star (or other astronomical object) is. Fainter stars
have larger magnitudes, such as 10.0. The bright star Vega is magnitude 0.0. Generally the
faintest star you can see with your eyes from a dark site is about magnitude 6.5 (although
many experienced observers can in fact see fainter). A few stars, such as Sirius, and some
planets are brighter than Vega. These have negative magnitude numbers. For instance the
magnitude of Sirius is -1.5.
Minor Planet - a small rocky or icy body orbiting the sun that doesn't display a coma or tail
like a comet. Asteroids are a type of minor planet that are mostly found between the orbits
of Mars and Jupiter in the so-called asteroid belt. Other types of minor planets are Near
Earth Objects and Kuiper Belt objects.
Multiple Star -- also known as a double star or double star system. This is one or more
stars that are very close together in the sky. Some just happen to appear close to one
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another. Others are physically connected by gravity, orbiting about one another. In the
eyepiece some double stars are widely separated, while others are so close that they appear
blended together. Still other are so close together that they look like a single star.
Naked Eye Limiting Magnitude – the magnitude of the faintest star that can be seen with
the unaided eye nearly overhead. This magnitude characterizes the light pollution of an
observing location.
Nova - a star that brightens suddenly for a period of time.
Open Cluster - a cluster of stars, usually in our own galaxy. These clusters of stars have
fewer stars that are more loosely spread than the Globular star clusters. A typical open
cluster has a few dozen to a few hundred stars in it. Most open clusters are found along the
Milky Way. . E.g. The Pleiades.
Planet - an object that orbits the sun that is massive enough to have cleared its orbit of
most smaller bodies. The planets in our solar system are: Mercury, Venus, Earth, Mars,
Jupiter, Saturn, Uranus and Neptune.
Planet Satellite - or moon, a smaller natural object that orbits another planet such as
Jupiter. E.g. Io, Europa, Callisto, and Ganymede are large satellites of Jupiter.
Planetary Nebula - a small cloud of glowing gas created by a star that is expelling its
atmosphere into space around it. The Ring Nebula is the most well-known example.
Right Ascension – measured eastward on the celestial sphere from the vernal equinox,
parallel to the celestial equator, much like longitude on the earth. Often abbreviated as
R.A., it is measured in hours, minutes and seconds. All the way around the sky once is 24
hours of RA.
Star - a condensed ball of gas that shines brightly due to fusion. Our sun is a star. The
other stars are so far away that they appear as points of light in even the largest telescope.
Solar System - one or more stars (and in many cases planets) connected by gravity. Our
own solar system consists of the sun (a star), planets, asteroids, and comets. In recent
years many other stars have also been found to have planets, forming other solar systems.
Supernova - a massive star that explodes, suddenly brightening enormously, often
outshining the combined light of all the stars in an entire galaxy. Most supernovas are seen
in other galaxies. Although estimated to occur once every 50 years, the last supernova in
our own Milky Way galaxy was seen in 1604.
Quasar - the very bright core of a distant galaxy. Quasars look like faint stars in a
telescope. Only a handful are in range of telescopes smaller than 6 inches. E.g. 3C 273.
Zenith - the point in the sky directly above the observer.
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